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	$92.25	7.826%	$99.4695	$99.47	$99.45	$99.50
Purchase #2	$170.55	3.343%	$176.2515	$176.25	$176.25	$176.30
Purchase #3	$208.33	6.305%	$221.4652	$221.47	$221.45	$221.50
Purchase #4	$47.45	6.690%	$50.6244	$50.62	$50.60	$50.60
Purchase #5	$250.48	7.551%	$269.3937	$269.39	$269.40	$269.40
Purchase #6	$211.31	11.303%	$235.1944	$235.19	$235.20	$235.20
Purchase #7	$42.89	5.330%	$45.176	$45.18	$45.20	$45.20
7 purchase totals =	$1,023.26		$1,097.5747	$1,097.57	$1,097.55	$1,097.70