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	$157.96	8.477%	$171.3503	$171.35	$171.35	$171.40
Purchase #2	$42.61	12.102%	$47.7667	$47.77	$47.75	$47.80
Purchase #3	$180.57	10.806%	$200.0824	$200.08	$200.10	$200.10
Purchase #4	$104.47	7.263%	$112.0577	$112.06	$112.05	$112.10
Purchase #5	$122.80	4.528%	$128.3604	$128.36	$128.35	$128.40
Purchase #6	$160.36	7.359%	$172.1609	$172.16	$172.15	$172.20
Purchase #7	$104.61	4.588%	$109.4095	$109.41	$109.40	$109.40
7 purchase totals =	$873.38		$941.1879	$941.19	$941.15	$941.40