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	$89.67	7.134%	$96.0671	$96.07	$96.05	$96.10
Purchase #2	$163.78	7.156%	$175.5001	$175.50	$175.50	$175.50
Purchase #3	$56.53	10.616%	$62.5312	$62.53	$62.55	$62.50
Purchase #4	$28.33	13.562%	$32.1721	$32.17	$32.15	$32.20
Purchase #5	$53.86	10.673%	$59.6085	$59.61	$59.60	$59.60
Purchase #6	$37.99	5.513%	$40.0844	$40.08	$40.10	$40.10
Purchase #7	$56.64	9.430%	$61.9812	$61.98	$62.00	$62.00
7 purchase totals =	$486.80		$527.9446	$527.94	$527.95	$528.00