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	$188.90	12.629%	$212.7562	$212.76	$212.75	$212.80
Purchase #2	$18.36	11.672%	$20.503	$20.50	$20.50	$20.50
Purchase #3	$73.76	9.627%	$80.8609	$80.86	$80.85	$80.90
Purchase #4	$135.92	9.130%	$148.3295	$148.33	$148.35	$148.30
Purchase #5	$58.69	13.874%	$66.8327	$66.83	$66.85	$66.80
Purchase #6	$171.63	7.777%	$184.9777	$184.98	$185.00	$185.00
Purchase #7	$98.50	5.646%	$104.0613	$104.06	$104.05	$104.10
7 purchase totals =	$745.76		$818.3213	$818.32	$818.35	$818.40