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	$82.96	8.121%	$89.6972	$89.70	$89.70	$89.70
Purchase #2	$50.81	8.478%	$55.1177	$55.12	$55.10	$55.10
Purchase #3	$202.86	9.529%	$222.1905	$222.19	$222.20	$222.20
Purchase #4	$149.82	4.704%	$156.8675	$156.87	$156.85	$156.90
Purchase #5	$93.75	8.611%	$101.8228	$101.82	$101.80	$101.80
Purchase #6	$82.73	9.711%	$90.7639	$90.76	$90.75	$90.80
Purchase #7	$154.33	4.350%	$161.0434	$161.04	$161.05	$161.00
7 purchase totals =	$817.26		$877.5030	$877.50	$877.45	$877.50