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	$104.86	8.591%	$113.8685	$113.87	$113.85	$113.90
Purchase #2	$211.39	8.572%	$229.5104	$229.51	$229.50	$229.50
Purchase #3	$174.46	11.344%	$194.2507	$194.25	$194.25	$194.30
Purchase #4	$212.54	13.285%	$240.7759	$240.78	$240.80	$240.80
Purchase #5	$6.25	10.311%	$6.8944	$6.89	$6.90	$6.90
Purchase #6	$55.83	8.820%	$60.7542	$60.75	$60.75	$60.80
Purchase #7	$152.86	12.230%	$171.5548	$171.55	$171.55	$171.60
7 purchase totals =	$918.19		$1,017.6089	$1,017.60	$1,017.60	$1,017.80