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	$32.64	4.479%	$34.1019	$34.10	$34.10	$34.10
Purchase #2	$99.28	12.231%	$111.4229	$111.42	$111.40	$111.40
Purchase #3	$124.48	12.279%	$139.7649	$139.76	$139.75	$139.80
Purchase #4	$170.39	6.591%	$181.6204	$181.62	$181.60	$181.60
Purchase #5	$6.66	4.590%	$6.9657	$6.97	$6.95	$7.00
Purchase #6	$187.90	4.412%	$196.1901	$196.19	$196.20	$196.20
Purchase #7	$51.51	7.643%	$55.4469	$55.45	$55.45	$55.40
7 purchase totals =	$672.86		$725.5128	$725.51	$725.45	$725.50