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	$83.75	13.711%	$95.233	$95.23	$95.25	$95.20
Purchase #2	$216.87	9.109%	$236.6247	$236.62	$236.60	$236.60
Purchase #3	$200.96	7.342%	$215.7145	$215.71	$215.70	$215.70
Purchase #4	$179.94	11.383%	$200.4226	$200.42	$200.40	$200.40
Purchase #5	$164.78	12.775%	$185.8306	$185.83	$185.85	$185.80
Purchase #6	$232.78	13.470%	$264.1355	$264.14	$264.15	$264.10
Purchase #7	$118.98	13.808%	$135.4088	$135.41	$135.40	$135.40
7 purchase totals =	$1,198.06		$1,333.3697	$1,333.36	$1,333.35	$1,333.20