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	$150.74	11.133%	$167.5219	$167.52	$167.50	$167.50
Purchase #2	$79.84	4.457%	$83.3985	$83.40	$83.40	$83.40
Purchase #3	$33.43	12.731%	$37.686	$37.69	$37.70	$37.70
Purchase #4	$33.62	7.228%	$36.0501	$36.05	$36.05	$36.10
Purchase #5	$28.42	12.538%	$31.9833	$31.98	$32.00	$32.00
Purchase #6	$106.84	3.740%	$110.8358	$110.84	$110.85	$110.80
Purchase #7	$61.57	6.320%	$65.4612	$65.46	$65.45	$65.50
7 purchase totals =	$494.46		$532.9368	$532.94	$532.95	$533.00