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	$63.42	6.755%	$67.704	$67.70	$67.70	$67.70
Purchase #2	$187.76	8.749%	$204.1871	$204.19	$204.20	$204.20
Purchase #3	$94.78	5.701%	$100.1834	$100.18	$100.20	$100.20
Purchase #4	$250.86	7.860%	$270.5776	$270.58	$270.60	$270.60
Purchase #5	$165.65	13.721%	$188.3788	$188.38	$188.40	$188.40
Purchase #6	$177.43	9.778%	$194.7791	$194.78	$194.80	$194.80
Purchase #7	$33.43	7.155%	$35.8219	$35.82	$35.80	$35.80
7 purchase totals =	$973.33		$1,061.6319	$1,061.63	$1,061.70	$1,061.70