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	$108.67	4.835%	$113.9242	$113.92	$113.90	$113.90
Purchase #2	$57.75	8.104%	$62.4301	$62.43	$62.45	$62.40
Purchase #3	$200.55	12.409%	$225.4362	$225.44	$225.45	$225.40
Purchase #4	$245.48	7.756%	$264.5194	$264.52	$264.50	$264.50
Purchase #5	$89.45	4.798%	$93.7418	$93.74	$93.75	$93.70
Purchase #6	$67.62	5.575%	$71.3898	$71.39	$71.40	$71.40
Purchase #7	$137.80	10.535%	$152.3172	$152.32	$152.30	$152.30
7 purchase totals =	$907.32		$983.7587	$983.76	$983.75	$983.60