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	$168.94	3.210%	$174.363	$174.36	$174.35	$174.40
Purchase #2	$85.25	8.192%	$92.2337	$92.23	$92.25	$92.20
Purchase #3	$146.52	3.631%	$151.8401	$151.84	$151.85	$151.80
Purchase #4	$188.94	5.794%	$199.8872	$199.89	$199.90	$199.90
Purchase #5	$239.39	10.550%	$264.6456	$264.65	$264.65	$264.60
Purchase #6	$234.95	11.789%	$262.6483	$262.65	$262.65	$262.60
Purchase #7	$29.90	12.713%	$33.7012	$33.70	$33.70	$33.70
7 purchase totals =	$1,093.89		$1,179.3191	$1,179.32	$1,179.35	$1,179.20