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	$173.98	6.439%	$185.1826	$185.18	$185.20	$185.20
Purchase #2	$174.46	12.787%	$196.7682	$196.77	$196.75	$196.80
Purchase #3	$5.84	5.319%	$6.1506	$6.15	$6.15	$6.20
Purchase #4	$232.62	9.665%	$255.1027	$255.10	$255.10	$255.10
Purchase #5	$120.45	9.201%	$131.5326	$131.53	$131.55	$131.50
Purchase #6	$140.44	8.187%	$151.9378	$151.94	$151.95	$151.90
Purchase #7	$148.95	5.593%	$157.2808	$157.28	$157.30	$157.30
7 purchase totals =	$996.74		$1,083.9553	$1,083.95	$1,084.00	$1,084.00