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	$85.90	12.120%	$96.3111	$96.31	$96.30	$96.30
Purchase #2	$56.39	9.398%	$61.6895	$61.69	$61.70	$61.70
Purchase #3	$177.52	7.433%	$190.7151	$190.72	$190.70	$190.70
Purchase #4	$203.38	12.164%	$228.1191	$228.12	$228.10	$228.10
Purchase #5	$135.62	11.674%	$151.4523	$151.45	$151.45	$151.50
Purchase #6	$150.70	5.602%	$159.1422	$159.14	$159.15	$159.10
Purchase #7	$68.77	5.806%	$72.7628	$72.76	$72.75	$72.80
7 purchase totals =	$878.28		$960.1921	$960.19	$960.15	$960.20