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	$172.41	11.223%	$191.7596	$191.76	$191.75	$191.80
Purchase #2	$131.47	7.347%	$141.1291	$141.13	$141.15	$141.10
Purchase #3	$182.78	12.448%	$205.5325	$205.53	$205.55	$205.50
Purchase #4	$56.94	7.733%	$61.3432	$61.34	$61.35	$61.30
Purchase #5	$185.28	7.529%	$199.2297	$199.23	$199.25	$199.20
Purchase #6	$101.87	12.503%	$114.6068	$114.61	$114.60	$114.60
Purchase #7	$190.63	4.789%	$199.7593	$199.76	$199.75	$199.80
7 purchase totals =	$1,021.38		$1,113.3602	$1,113.36	$1,113.40	$1,113.30