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	$191.53	9.709%	$210.1256	$210.13	$210.15	$210.10
Purchase #2	$210.37	11.151%	$233.8284	$233.83	$233.85	$233.80
Purchase #3	$182.69	9.375%	$199.8172	$199.82	$199.80	$199.80
Purchase #4	$132.35	6.715%	$141.2373	$141.24	$141.25	$141.20
Purchase #5	$121.31	4.730%	$127.048	$127.05	$127.05	$127.00
Purchase #6	$143.71	13.386%	$162.947	$162.95	$162.95	$162.90
Purchase #7	$205.93	11.461%	$229.5316	$229.53	$229.55	$229.50
7 purchase totals =	$1,187.89		$1,304.5351	$1,304.55	$1,304.60	$1,304.30