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	$53.88	13.156%	$60.9685	$60.97	$60.95	$61.00
Purchase #2	$32.33	3.245%	$33.3791	$33.38	$33.40	$33.40
Purchase #3	$50.84	8.469%	$55.1456	$55.15	$55.15	$55.10
Purchase #4	$108.30	11.227%	$120.4588	$120.46	$120.45	$120.50
Purchase #5	$76.43	3.214%	$78.8865	$78.89	$78.90	$78.90
Purchase #6	$20.37	9.164%	$22.2367	$22.24	$22.25	$22.20
Purchase #7	$54.96	4.512%	$57.4398	$57.44	$57.45	$57.40
7 purchase totals =	$397.11		$428.5150	$428.53	$428.55	$428.50