Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$121.69	4.593%	$127.2792	$127.28	$127.30	$127.30
Purchase #2	$163.64	11.524%	$182.4979	$182.50	$182.50	$182.50
Purchase #3	$154.41	13.632%	$175.4592	$175.46	$175.45	$175.50
Purchase #4	$165.41	3.110%	$170.5543	$170.55	$170.55	$170.60
Purchase #5	$231.94	7.253%	$248.7626	$248.76	$248.75	$248.80
Purchase #6	$183.98	10.785%	$203.8222	$203.82	$203.80	$203.80
Purchase #7	$183.71	6.693%	$196.0057	$196.01	$196.00	$196.00
7 purchase totals =	$1,204.78		$1,304.3811	$1,304.38	$1,304.35	$1,304.50