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	$152.68	13.206%	$172.8429	$172.84	$172.85	$172.80
Purchase #2	$159.88	5.633%	$168.886	$168.89	$168.90	$168.90
Purchase #3	$113.27	12.528%	$127.4605	$127.46	$127.45	$127.50
Purchase #4	$116.33	7.457%	$125.0047	$125.00	$125.00	$125.00
Purchase #5	$9.47	13.296%	$10.7291	$10.73	$10.75	$10.70
Purchase #6	$178.69	11.787%	$199.7522	$199.75	$199.75	$199.80
Purchase #7	$43.86	13.359%	$49.7193	$49.72	$49.70	$49.70
7 purchase totals =	$774.18		$854.3947	$854.39	$854.40	$854.40