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	$168.90	11.695%	$188.6529	$188.65	$188.65	$188.70
Purchase #2	$30.32	10.169%	$33.4032	$33.40	$33.40	$33.40
Purchase #3	$143.72	11.621%	$160.4217	$160.42	$160.40	$160.40
Purchase #4	$94.82	6.758%	$101.2279	$101.23	$101.25	$101.20
Purchase #5	$183.94	12.293%	$206.5517	$206.55	$206.55	$206.60
Purchase #6	$51.52	7.601%	$55.436	$55.44	$55.45	$55.40
Purchase #7	$61.50	10.487%	$67.9495	$67.95	$67.95	$67.90
7 purchase totals =	$734.72		$813.6429	$813.64	$813.65	$813.60