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	$94.76	6.824%	$101.2264	$101.23	$101.25	$101.20
Purchase #2	$20.40	5.533%	$21.5287	$21.53	$21.55	$21.50
Purchase #3	$63.65	10.172%	$70.1245	$70.12	$70.10	$70.10
Purchase #4	$142.64	11.818%	$159.4972	$159.50	$159.50	$159.50
Purchase #5	$75.35	7.193%	$80.7699	$80.77	$80.75	$80.80
Purchase #6	$89.82	5.236%	$94.523	$94.52	$94.50	$94.50
Purchase #7	$61.57	9.428%	$67.3748	$67.37	$67.35	$67.40
7 purchase totals =	$548.19		$595.0445	$595.04	$595.00	$595.00