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	$171.82	8.106%	$185.7477	$185.75	$185.75	$185.70
Purchase #2	$95.66	11.596%	$106.7527	$106.75	$106.75	$106.80
Purchase #3	$21.25	5.860%	$22.4953	$22.50	$22.50	$22.50
Purchase #4	$100.64	10.351%	$111.0572	$111.06	$111.05	$111.10
Purchase #5	$47.40	12.700%	$53.4198	$53.42	$53.40	$53.40
Purchase #6	$111.91	6.434%	$119.1103	$119.11	$119.10	$119.10
Purchase #7	$84.90	12.442%	$95.4633	$95.46	$95.45	$95.50
7 purchase totals =	$633.58		$694.0463	$694.05	$694.00	$694.10