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	$250.89	4.237%	$261.5202	$261.52	$261.50	$261.50
Purchase #2	$207.68	10.287%	$229.044	$229.04	$229.05	$229.00
Purchase #3	$137.68	8.149%	$148.8995	$148.90	$148.90	$148.90
Purchase #4	$82.41	11.354%	$91.7668	$91.77	$91.75	$91.80
Purchase #5	$76.76	6.286%	$81.5851	$81.59	$81.60	$81.60
Purchase #6	$67.36	5.851%	$71.3012	$71.30	$71.30	$71.30
Purchase #7	$109.80	12.540%	$123.5689	$123.57	$123.55	$123.60
7 purchase totals =	$932.58		$1,007.6857	$1,007.69	$1,007.65	$1,007.70