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	$191.76	8.701%	$208.445	$208.45	$208.45	$208.40
Purchase #2	$56.56	10.601%	$62.5559	$62.56	$62.55	$62.60
Purchase #3	$209.44	5.791%	$221.5687	$221.57	$221.55	$221.60
Purchase #4	$18.66	12.127%	$20.9229	$20.92	$20.90	$20.90
Purchase #5	$157.75	10.443%	$174.2238	$174.22	$174.20	$174.20
Purchase #6	$235.35	3.201%	$242.8836	$242.88	$242.90	$242.90
Purchase #7	$103.36	5.325%	$108.8639	$108.86	$108.85	$108.90
7 purchase totals =	$972.88		$1,039.4638	$1,039.46	$1,039.40	$1,039.50