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	$85.62	6.443%	$91.1365	$91.14	$91.15	$91.10
Purchase #2	$75.75	13.735%	$86.1543	$86.15	$86.15	$86.20
Purchase #3	$106.28	4.728%	$111.3049	$111.30	$111.30	$111.30
Purchase #4	$116.84	8.287%	$126.5225	$126.52	$126.50	$126.50
Purchase #5	$221.74	7.541%	$238.4614	$238.46	$238.45	$238.50
Purchase #6	$191.84	4.710%	$200.8757	$200.88	$200.90	$200.90
Purchase #7	$16.51	8.343%	$17.8874	$17.89	$17.90	$17.90
7 purchase totals =	$814.58		$872.3427	$872.34	$872.35	$872.40