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	$48.75	9.496%	$53.3793	$53.38	$53.40	$53.40
Purchase #2	$244.97	7.612%	$263.6171	$263.62	$263.60	$263.60
Purchase #3	$167.87	7.236%	$180.0171	$180.02	$180.00	$180.00
Purchase #4	$41.72	7.823%	$44.9838	$44.98	$45.00	$45.00
Purchase #5	$64.88	8.601%	$70.4603	$70.46	$70.45	$70.50
Purchase #6	$248.92	10.600%	$275.3055	$275.31	$275.30	$275.30
Purchase #7	$164.25	9.352%	$179.6107	$179.61	$179.60	$179.60
7 purchase totals =	$981.36		$1,067.3738	$1,067.38	$1,067.35	$1,067.40