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	$177.43	11.659%	$198.1166	$198.12	$198.10	$198.10
Purchase #2	$235.38	8.810%	$256.117	$256.12	$256.10	$256.10
Purchase #3	$98.72	12.813%	$111.369	$111.37	$111.35	$111.40
Purchase #4	$110.36	13.303%	$125.0412	$125.04	$125.05	$125.00
Purchase #5	$48.62	5.622%	$51.3534	$51.35	$51.35	$51.40
Purchase #6	$85.48	8.585%	$92.8185	$92.82	$92.80	$92.80
Purchase #7	$162.47	3.777%	$168.6065	$168.61	$168.60	$168.60
7 purchase totals =	$918.46		$1,003.4222	$1,003.43	$1,003.35	$1,003.40