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	$162.55	6.518%	$173.145	$173.15	$173.15	$173.10
Purchase #2	$241.47	3.588%	$250.1339	$250.13	$250.15	$250.10
Purchase #3	$59.26	4.130%	$61.7074	$61.71	$61.70	$61.70
Purchase #4	$200.34	10.277%	$220.9289	$220.93	$220.95	$220.90
Purchase #5	$45.40	5.185%	$47.754	$47.75	$47.75	$47.80
Purchase #6	$249.89	13.774%	$284.3098	$284.31	$284.30	$284.30
Purchase #7	$238.67	10.154%	$262.9046	$262.90	$262.90	$262.90
7 purchase totals =	$1,197.58		$1,300.8836	$1,300.88	$1,300.90	$1,300.80