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	$168.95	5.137%	$177.629	$177.63	$177.65	$177.60
Purchase #2	$57.26	7.372%	$61.4812	$61.48	$61.50	$61.50
Purchase #3	$51.80	4.445%	$54.1025	$54.10	$54.10	$54.10
Purchase #4	$151.82	4.849%	$159.1818	$159.18	$159.20	$159.20
Purchase #5	$193.35	12.168%	$216.8768	$216.88	$216.90	$216.90
Purchase #6	$39.78	9.529%	$43.5706	$43.57	$43.55	$43.60
Purchase #7	$61.77	9.368%	$67.5566	$67.56	$67.55	$67.60
7 purchase totals =	$724.73		$780.3985	$780.40	$780.45	$780.50