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	$150.68	9.772%	$165.4044	$165.40	$165.40	$165.40
Purchase #2	$67.67	7.312%	$72.618	$72.62	$72.60	$72.60
Purchase #3	$187.59	6.294%	$199.3969	$199.40	$199.40	$199.40
Purchase #4	$239.76	11.132%	$266.4501	$266.45	$266.45	$266.50
Purchase #5	$224.64	3.405%	$232.289	$232.29	$232.30	$232.30
Purchase #6	$138.46	11.873%	$154.8994	$154.90	$154.90	$154.90
Purchase #7	$49.94	11.113%	$55.4898	$55.49	$55.50	$55.50
7 purchase totals =	$1,058.74		$1,146.5476	$1,146.55	$1,146.55	$1,146.60