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	$224.27	6.801%	$239.5226	$239.52	$239.50	$239.50
Purchase #2	$96.67	7.297%	$103.724	$103.72	$103.70	$103.70
Purchase #3	$204.50	8.345%	$221.5655	$221.57	$221.55	$221.60
Purchase #4	$89.34	13.821%	$101.6877	$101.69	$101.70	$101.70
Purchase #5	$163.88	12.200%	$183.8734	$183.87	$183.85	$183.90
Purchase #6	$36.82	4.557%	$38.4979	$38.50	$38.50	$38.50
Purchase #7	$164.34	6.689%	$175.3327	$175.33	$175.35	$175.30
7 purchase totals =	$979.82		$1,064.2038	$1,064.20	$1,064.15	$1,064.20