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	$66.66	9.745%	$73.156	$73.16	$73.15	$73.20
Purchase #2	$79.26	9.217%	$86.5654	$86.57	$86.55	$86.60
Purchase #3	$86.68	13.738%	$98.5881	$98.59	$98.60	$98.60
Purchase #4	$57.83	6.226%	$61.4305	$61.43	$61.45	$61.40
Purchase #5	$232.28	4.333%	$242.3447	$242.34	$242.35	$242.30
Purchase #6	$14.91	5.267%	$15.6953	$15.70	$15.70	$15.70
Purchase #7	$80.83	10.776%	$89.5402	$89.54	$89.55	$89.50
7 purchase totals =	$618.45		$667.3202	$667.33	$667.35	$667.30