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	$104.27	13.497%	$118.3433	$118.34	$118.35	$118.30
Purchase #2	$101.91	5.141%	$107.1492	$107.15	$107.15	$107.10
Purchase #3	$91.45	13.157%	$103.4821	$103.48	$103.50	$103.50
Purchase #4	$65.56	6.488%	$69.8135	$69.81	$69.80	$69.80
Purchase #5	$171.80	12.169%	$192.7063	$192.71	$192.70	$192.70
Purchase #6	$32.74	3.139%	$33.7677	$33.77	$33.75	$33.80
Purchase #7	$95.41	8.297%	$103.3262	$103.33	$103.35	$103.30
7 purchase totals =	$663.14		$728.5883	$728.59	$728.60	$728.50