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	$172.37	10.229%	$190.0017	$190.00	$190.00	$190.00
Purchase #2	$42.28	12.463%	$47.5494	$47.55	$47.55	$47.50
Purchase #3	$51.70	4.787%	$54.1749	$54.17	$54.15	$54.20
Purchase #4	$7.54	12.367%	$8.4725	$8.47	$8.45	$8.50
Purchase #5	$28.44	4.677%	$29.7701	$29.77	$29.75	$29.80
Purchase #6	$65.45	10.714%	$72.4623	$72.46	$72.45	$72.50
Purchase #7	$70.94	6.154%	$75.3056	$75.31	$75.30	$75.30
7 purchase totals =	$438.72		$477.7365	$477.73	$477.65	$477.80