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	$125.31	13.423%	$142.1304	$142.13	$142.15	$142.10
Purchase #2	$147.79	12.539%	$166.3214	$166.32	$166.30	$166.30
Purchase #3	$24.53	13.368%	$27.8092	$27.81	$27.80	$27.80
Purchase #4	$50.36	7.563%	$54.1687	$54.17	$54.15	$54.20
Purchase #5	$228.30	12.457%	$256.7393	$256.74	$256.75	$256.70
Purchase #6	$222.66	12.595%	$250.704	$250.70	$250.70	$250.70
Purchase #7	$109.80	3.345%	$113.4728	$113.47	$113.45	$113.50
7 purchase totals =	$908.75		$1,011.3458	$1,011.34	$1,011.30	$1,011.30