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	$118.76	4.448%	$124.0424	$124.04	$124.05	$124.00
Purchase #2	$85.41	4.333%	$89.1108	$89.11	$89.10	$89.10
Purchase #3	$9.95	4.410%	$10.3888	$10.39	$10.40	$10.40
Purchase #4	$42.39	12.181%	$47.5535	$47.55	$47.55	$47.60
Purchase #5	$34.91	4.793%	$36.5832	$36.58	$36.60	$36.60
Purchase #6	$91.89	8.602%	$99.7944	$99.79	$99.80	$99.80
Purchase #7	$166.89	13.200%	$188.9195	$188.92	$188.90	$188.90
7 purchase totals =	$550.20		$596.3926	$596.38	$596.40	$596.40