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	$85.82	12.176%	$96.2694	$96.27	$96.25	$96.30
Purchase #2	$37.25	6.457%	$39.6552	$39.66	$39.65	$39.70
Purchase #3	$222.54	6.830%	$237.7395	$237.74	$237.75	$237.70
Purchase #4	$223.86	9.677%	$245.5229	$245.52	$245.50	$245.50
Purchase #5	$9.55	6.828%	$10.2021	$10.20	$10.20	$10.20
Purchase #6	$67.36	9.764%	$73.937	$73.94	$73.95	$73.90
Purchase #7	$79.92	12.108%	$89.5967	$89.60	$89.60	$89.60
7 purchase totals =	$726.30		$792.9228	$792.93	$792.90	$792.90