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	$95.54	12.470%	$107.4538	$107.45	$107.45	$107.50
Purchase #2	$247.96	6.572%	$264.2559	$264.26	$264.25	$264.30
Purchase #3	$40.32	7.223%	$43.2323	$43.23	$43.25	$43.20
Purchase #4	$13.63	6.527%	$14.5196	$14.52	$14.50	$14.50
Purchase #5	$65.36	10.614%	$72.2973	$72.30	$72.30	$72.30
Purchase #6	$9.39	11.836%	$10.5014	$10.50	$10.50	$10.50
Purchase #7	$47.35	4.196%	$49.3368	$49.34	$49.35	$49.30
7 purchase totals =	$519.55		$561.5971	$561.60	$561.60	$561.60