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	$94.43	9.118%	$103.0401	$103.04	$103.05	$103.00
Purchase #2	$212.66	3.385%	$219.8585	$219.86	$219.85	$219.90
Purchase #3	$246.45	4.753%	$258.1638	$258.16	$258.15	$258.20
Purchase #4	$24.85	9.223%	$27.1419	$27.14	$27.15	$27.10
Purchase #5	$108.36	3.107%	$111.7267	$111.73	$111.75	$111.70
Purchase #6	$161.72	13.260%	$183.1641	$183.16	$183.15	$183.20
Purchase #7	$225.42	7.700%	$242.7773	$242.78	$242.80	$242.80
7 purchase totals =	$1,073.89		$1,145.8724	$1,145.87	$1,145.90	$1,145.90