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	$92.40	3.825%	$95.9343	$95.93	$95.95	$95.90
Purchase #2	$83.98	6.306%	$89.2758	$89.28	$89.30	$89.30
Purchase #3	$210.54	11.871%	$235.5332	$235.53	$235.55	$235.50
Purchase #4	$109.86	8.753%	$119.476	$119.48	$119.50	$119.50
Purchase #5	$33.98	10.286%	$37.4752	$37.48	$37.50	$37.50
Purchase #6	$211.92	5.550%	$223.6816	$223.68	$223.70	$223.70
Purchase #7	$130.74	6.262%	$138.9269	$138.93	$138.95	$138.90
7 purchase totals =	$873.42		$940.3030	$940.31	$940.45	$940.30