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	$187.69	4.726%	$196.5602	$196.56	$196.55	$196.60
Purchase #2	$248.71	6.459%	$264.7742	$264.77	$264.75	$264.80
Purchase #3	$235.34	8.318%	$254.9156	$254.92	$254.90	$254.90
Purchase #4	$238.55	8.723%	$259.3587	$259.36	$259.35	$259.40
Purchase #5	$245.27	13.230%	$277.7192	$277.72	$277.70	$277.70
Purchase #6	$54.98	8.836%	$59.838	$59.84	$59.85	$59.80
Purchase #7	$157.82	10.515%	$174.4148	$174.41	$174.40	$174.40
7 purchase totals =	$1,368.36		$1,487.5807	$1,487.58	$1,487.50	$1,487.60