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	$197.90	11.578%	$220.8129	$220.81	$220.80	$220.80
Purchase #2	$105.51	5.742%	$111.5684	$111.57	$111.55	$111.60
Purchase #3	$79.55	12.608%	$89.5797	$89.58	$89.60	$89.60
Purchase #4	$73.68	10.397%	$81.3405	$81.34	$81.35	$81.30
Purchase #5	$91.97	7.629%	$98.9864	$98.99	$99.00	$99.00
Purchase #6	$60.27	8.680%	$65.5014	$65.50	$65.50	$65.50
Purchase #7	$80.37	6.465%	$85.5659	$85.57	$85.55	$85.60
7 purchase totals =	$689.25		$753.3552	$753.36	$753.35	$753.40