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	$231.77	13.180%	$262.3173	$262.32	$262.30	$262.30
Purchase #2	$80.79	11.347%	$89.9572	$89.96	$89.95	$90.00
Purchase #3	$160.31	6.813%	$171.2319	$171.23	$171.25	$171.20
Purchase #4	$132.45	12.298%	$148.7387	$148.74	$148.75	$148.70
Purchase #5	$85.71	6.129%	$90.9632	$90.96	$90.95	$91.00
Purchase #6	$74.86	6.355%	$79.6174	$79.62	$79.60	$79.60
Purchase #7	$161.75	4.739%	$169.4153	$169.42	$169.40	$169.40
7 purchase totals =	$927.64		$1,012.2410	$1,012.25	$1,012.20	$1,012.20