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	$212.73	7.594%	$228.8847	$228.88	$228.90	$228.90
Purchase #2	$184.86	11.605%	$206.313	$206.31	$206.30	$206.30
Purchase #3	$53.83	9.713%	$59.0585	$59.06	$59.05	$59.10
Purchase #4	$212.28	6.180%	$225.3989	$225.40	$225.40	$225.40
Purchase #5	$33.67	6.395%	$35.8232	$35.82	$35.80	$35.80
Purchase #6	$168.93	9.482%	$184.9479	$184.95	$184.95	$184.90
Purchase #7	$41.74	3.617%	$43.2497	$43.25	$43.25	$43.20
7 purchase totals =	$908.04		$983.6759	$983.67	$983.65	$983.60