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	$151.45	10.833%	$167.8566	$167.86	$167.85	$167.90
Purchase #2	$121.91	5.760%	$128.932	$128.93	$128.95	$128.90
Purchase #3	$194.65	8.364%	$210.9305	$210.93	$210.95	$210.90
Purchase #4	$134.88	13.119%	$152.5749	$152.57	$152.55	$152.60
Purchase #5	$71.73	9.196%	$78.3263	$78.33	$78.35	$78.30
Purchase #6	$24.93	12.306%	$27.9979	$28.00	$28.00	$28.00
Purchase #7	$16.78	11.247%	$18.6672	$18.67	$18.65	$18.70
7 purchase totals =	$716.33		$785.2854	$785.29	$785.30	$785.30