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	$72.52	11.495%	$80.8562	$80.86	$80.85	$80.90
Purchase #2	$162.72	13.174%	$184.1567	$184.16	$184.15	$184.20
Purchase #3	$240.87	6.121%	$255.6137	$255.61	$255.60	$255.60
Purchase #4	$250.57	4.264%	$261.2543	$261.25	$261.25	$261.30
Purchase #5	$98.64	11.178%	$109.666	$109.67	$109.65	$109.70
Purchase #6	$122.48	4.648%	$128.1729	$128.17	$128.15	$128.20
Purchase #7	$93.71	10.541%	$103.588	$103.59	$103.60	$103.60
7 purchase totals =	$1,041.51		$1,123.3078	$1,123.31	$1,123.25	$1,123.50