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	$94.53	9.863%	$103.8535	$103.85	$103.85	$103.90
Purchase #2	$80.55	13.541%	$91.4573	$91.46	$91.45	$91.50
Purchase #3	$146.58	3.453%	$151.6414	$151.64	$151.65	$151.60
Purchase #4	$243.53	6.489%	$259.3327	$259.33	$259.35	$259.30
Purchase #5	$234.61	3.484%	$242.7838	$242.78	$242.80	$242.80
Purchase #6	$19.56	3.310%	$20.2074	$20.21	$20.20	$20.20
Purchase #7	$104.73	9.642%	$114.8281	$114.83	$114.85	$114.80
7 purchase totals =	$924.09		$984.1042	$984.10	$984.15	$984.10