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	$197.89	12.385%	$222.3987	$222.40	$222.40	$222.40
Purchase #2	$212.77	4.526%	$222.4	$222.40	$222.40	$222.40
Purchase #3	$46.25	6.684%	$49.3414	$49.34	$49.35	$49.30
Purchase #4	$9.50	11.533%	$10.5956	$10.60	$10.60	$10.60
Purchase #5	$168.63	8.780%	$183.4357	$183.44	$183.45	$183.40
Purchase #6	$39.88	8.502%	$43.2706	$43.27	$43.25	$43.30
Purchase #7	$53.78	8.860%	$58.5449	$58.54	$58.55	$58.50
7 purchase totals =	$728.70		$789.9869	$789.99	$790.00	$789.90