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	$171.63	9.713%	$188.3004	$188.30	$188.30	$188.30
Purchase #2	$111.25	4.172%	$115.8914	$115.89	$115.90	$115.90
Purchase #3	$34.89	6.428%	$37.1327	$37.13	$37.15	$37.10
Purchase #4	$213.94	4.278%	$223.0924	$223.09	$223.10	$223.10
Purchase #5	$181.49	13.584%	$206.1436	$206.14	$206.15	$206.10
Purchase #6	$30.84	3.281%	$31.8519	$31.85	$31.85	$31.90
Purchase #7	$128.67	9.263%	$140.5887	$140.59	$140.60	$140.60
7 purchase totals =	$872.71		$943.0011	$942.99	$943.05	$943.00