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	$136.84	11.605%	$152.7203	$152.72	$152.70	$152.70
Purchase #2	$192.83	10.132%	$212.3675	$212.37	$212.35	$212.40
Purchase #3	$142.53	6.164%	$151.3155	$151.32	$151.30	$151.30
Purchase #4	$184.60	6.575%	$196.7375	$196.74	$196.75	$196.70
Purchase #5	$162.84	4.587%	$170.3095	$170.31	$170.30	$170.30
Purchase #6	$183.28	7.684%	$197.3632	$197.36	$197.35	$197.40
Purchase #7	$76.98	11.582%	$85.8958	$85.90	$85.90	$85.90
7 purchase totals =	$1,079.90		$1,166.7093	$1,166.72	$1,166.65	$1,166.70