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	$208.31	13.398%	$236.2194	$236.22	$236.20	$236.20
Purchase #2	$245.49	12.140%	$275.2925	$275.29	$275.30	$275.30
Purchase #3	$98.38	4.727%	$103.0304	$103.03	$103.05	$103.00
Purchase #4	$72.30	7.148%	$77.468	$77.47	$77.45	$77.50
Purchase #5	$123.66	6.871%	$132.1567	$132.16	$132.15	$132.20
Purchase #6	$125.41	10.849%	$139.0157	$139.02	$139.00	$139.00
Purchase #7	$131.40	12.550%	$147.8907	$147.89	$147.90	$147.90
7 purchase totals =	$1,004.95		$1,111.0734	$1,111.08	$1,111.05	$1,111.10