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	$50.29	7.471%	$54.0472	$54.05	$54.05	$54.00
Purchase #2	$250.62	10.688%	$277.4063	$277.41	$277.40	$277.40
Purchase #3	$176.25	12.278%	$197.89	$197.89	$197.90	$197.90
Purchase #4	$147.96	13.642%	$168.1447	$168.14	$168.15	$168.10
Purchase #5	$238.61	10.260%	$263.0914	$263.09	$263.10	$263.10
Purchase #6	$64.63	4.550%	$67.5707	$67.57	$67.55	$67.60
Purchase #7	$139.71	8.138%	$151.0796	$151.08	$151.10	$151.10
7 purchase totals =	$1,068.07		$1,179.2299	$1,179.23	$1,179.25	$1,179.20