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	$212.31	4.420%	$221.6941	$221.69	$221.70	$221.70
Purchase #2	$34.91	7.233%	$37.435	$37.44	$37.45	$37.40
Purchase #3	$64.69	10.593%	$71.5426	$71.54	$71.55	$71.50
Purchase #4	$150.56	6.792%	$160.786	$160.79	$160.80	$160.80
Purchase #5	$83.78	5.102%	$88.0545	$88.05	$88.05	$88.10
Purchase #6	$88.82	5.337%	$93.5603	$93.56	$93.55	$93.60
Purchase #7	$23.75	5.541%	$25.066	$25.07	$25.05	$25.10
7 purchase totals =	$658.82		$698.1385	$698.14	$698.15	$698.20