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	$88.72	6.469%	$94.4593	$94.46	$94.45	$94.50
Purchase #2	$190.99	12.625%	$215.1025	$215.10	$215.10	$215.10
Purchase #3	$58.58	4.318%	$61.1095	$61.11	$61.10	$61.10
Purchase #4	$80.64	12.673%	$90.8595	$90.86	$90.85	$90.90
Purchase #5	$152.45	10.560%	$168.5487	$168.55	$168.55	$168.50
Purchase #6	$106.43	7.172%	$114.0632	$114.06	$114.05	$114.10
Purchase #7	$210.82	8.436%	$228.6048	$228.60	$228.60	$228.60
7 purchase totals =	$888.63		$972.7475	$972.74	$972.70	$972.80