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	$123.30	3.344%	$127.4232	$127.42	$127.40	$127.40
Purchase #2	$207.81	7.122%	$222.6102	$222.61	$222.60	$222.60
Purchase #3	$44.27	13.761%	$50.362	$50.36	$50.35	$50.40
Purchase #4	$188.47	11.428%	$210.0084	$210.01	$210.00	$210.00
Purchase #5	$73.30	7.740%	$78.9734	$78.97	$78.95	$79.00
Purchase #6	$71.35	7.657%	$76.8133	$76.81	$76.80	$76.80
Purchase #7	$244.88	10.458%	$270.4896	$270.49	$270.50	$270.50
7 purchase totals =	$953.38		$1,036.6801	$1,036.67	$1,036.60	$1,036.70