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	$233.76	13.387%	$265.0535	$265.05	$265.05	$265.10
Purchase #2	$212.46	10.832%	$235.4737	$235.47	$235.45	$235.50
Purchase #3	$32.31	3.465%	$33.4295	$33.43	$33.45	$33.40
Purchase #4	$147.25	11.453%	$164.1145	$164.11	$164.10	$164.10
Purchase #5	$164.75	9.770%	$180.8461	$180.85	$180.85	$180.80
Purchase #6	$84.90	4.745%	$88.9285	$88.93	$88.95	$88.90
Purchase #7	$32.48	4.362%	$33.8968	$33.90	$33.90	$33.90
7 purchase totals =	$907.91		$1,001.7426	$1,001.74	$1,001.75	$1,001.70