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	$160.77	7.761%	$173.2474	$173.25	$173.25	$173.20
Purchase #2	$107.68	5.321%	$113.4097	$113.41	$113.40	$113.40
Purchase #3	$52.73	13.655%	$59.9303	$59.93	$59.95	$59.90
Purchase #4	$59.93	8.277%	$64.8904	$64.89	$64.90	$64.90
Purchase #5	$39.92	13.742%	$45.4058	$45.41	$45.40	$45.40
Purchase #6	$98.93	5.518%	$104.389	$104.39	$104.40	$104.40
Purchase #7	$195.71	10.592%	$216.4396	$216.44	$216.45	$216.40
7 purchase totals =	$715.67		$777.7122	$777.72	$777.75	$777.60