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	$86.25	7.424%	$92.6532	$92.65	$92.65	$92.70
Purchase #2	$54.82	9.227%	$59.8782	$59.88	$59.90	$59.90
Purchase #3	$23.35	10.611%	$25.8277	$25.83	$25.85	$25.80
Purchase #4	$20.55	9.797%	$22.5633	$22.56	$22.55	$22.60
Purchase #5	$202.46	10.496%	$223.7102	$223.71	$223.70	$223.70
Purchase #6	$12.33	6.821%	$13.171	$13.17	$13.15	$13.20
Purchase #7	$207.43	4.602%	$216.9759	$216.98	$217.00	$217.00
7 purchase totals =	$607.19		$654.7795	$654.78	$654.80	$654.90