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	$74.47	12.611%	$83.8614	$83.86	$83.85	$83.90
Purchase #2	$206.92	9.648%	$226.8836	$226.88	$226.90	$226.90
Purchase #3	$5.77	11.396%	$6.4275	$6.43	$6.45	$6.40
Purchase #4	$97.27	7.261%	$104.3328	$104.33	$104.35	$104.30
Purchase #5	$79.29	12.285%	$89.0308	$89.03	$89.05	$89.00
Purchase #6	$57.52	6.331%	$61.1616	$61.16	$61.15	$61.20
Purchase #7	$170.46	10.736%	$188.7606	$188.76	$188.75	$188.80
7 purchase totals =	$691.70		$760.4583	$760.45	$760.50	$760.50