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	$178.56	3.793%	$185.3328	$185.33	$185.35	$185.30
Purchase #2	$232.55	8.177%	$251.5656	$251.57	$251.55	$251.60
Purchase #3	$212.94	12.369%	$239.2785	$239.28	$239.30	$239.30
Purchase #4	$57.95	5.702%	$61.2543	$61.25	$61.25	$61.30
Purchase #5	$63.87	12.426%	$71.8065	$71.81	$71.80	$71.80
Purchase #6	$60.54	11.104%	$67.2624	$67.26	$67.25	$67.30
Purchase #7	$160.44	7.603%	$172.6383	$172.64	$172.65	$172.60
7 purchase totals =	$966.85		$1,049.1384	$1,049.14	$1,049.15	$1,049.20