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	$200.83	12.488%	$225.9097	$225.91	$225.90	$225.90
Purchase #2	$65.88	4.166%	$68.6246	$68.62	$68.60	$68.60
Purchase #3	$58.30	5.701%	$61.6237	$61.62	$61.60	$61.60
Purchase #4	$60.93	7.154%	$65.2889	$65.29	$65.30	$65.30
Purchase #5	$162.40	11.614%	$181.2611	$181.26	$181.25	$181.30
Purchase #6	$159.51	4.234%	$166.2637	$166.26	$166.25	$166.30
Purchase #7	$236.79	4.375%	$247.1496	$247.15	$247.15	$247.10
7 purchase totals =	$944.64		$1,016.1213	$1,016.11	$1,016.05	$1,016.10