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	$125.72	12.821%	$141.8386	$141.84	$141.85	$141.80
Purchase #2	$219.60	7.296%	$235.622	$235.62	$235.60	$235.60
Purchase #3	$188.75	6.365%	$200.7639	$200.76	$200.75	$200.80
Purchase #4	$117.32	5.131%	$123.3397	$123.34	$123.35	$123.30
Purchase #5	$126.53	3.397%	$130.8282	$130.83	$130.85	$130.80
Purchase #6	$145.94	3.729%	$151.3821	$151.38	$151.40	$151.40
Purchase #7	$139.30	5.270%	$146.6411	$146.64	$146.65	$146.60
7 purchase totals =	$1,063.16		$1,130.4156	$1,130.41	$1,130.45	$1,130.30