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	$138.36	4.343%	$144.369	$144.37	$144.35	$144.40
Purchase #2	$135.73	10.349%	$149.7767	$149.78	$149.80	$149.80
Purchase #3	$196.47	5.123%	$206.5352	$206.54	$206.55	$206.50
Purchase #4	$248.70	10.448%	$274.6842	$274.68	$274.70	$274.70
Purchase #5	$100.46	6.401%	$106.8904	$106.89	$106.90	$106.90
Purchase #6	$40.49	8.124%	$43.7794	$43.78	$43.80	$43.80
Purchase #7	$115.38	10.554%	$127.5572	$127.56	$127.55	$127.60
7 purchase totals =	$975.59		$1,053.5921	$1,053.60	$1,053.65	$1,053.70