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	$41.54	10.453%	$45.8822	$45.88	$45.90	$45.90
Purchase #2	$29.87	12.243%	$33.527	$33.53	$33.55	$33.50
Purchase #3	$236.80	7.378%	$254.2711	$254.27	$254.25	$254.30
Purchase #4	$90.38	12.110%	$101.325	$101.33	$101.35	$101.30
Purchase #5	$110.26	3.790%	$114.4389	$114.44	$114.45	$114.40
Purchase #6	$240.76	13.700%	$273.7441	$273.74	$273.75	$273.70
Purchase #7	$73.51	5.394%	$77.4751	$77.48	$77.50	$77.50
7 purchase totals =	$823.12		$900.6634	$900.67	$900.75	$900.60