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	$171.54	10.130%	$188.917	$188.92	$188.90	$188.90
Purchase #2	$50.90	4.516%	$53.1986	$53.20	$53.20	$53.20
Purchase #3	$124.38	6.532%	$132.5045	$132.50	$132.50	$132.50
Purchase #4	$138.34	10.520%	$152.8934	$152.89	$152.90	$152.90
Purchase #5	$214.48	13.571%	$243.5871	$243.59	$243.60	$243.60
Purchase #6	$219.31	4.160%	$228.4333	$228.43	$228.45	$228.40
Purchase #7	$194.78	7.814%	$210.0001	$210.00	$210.00	$210.00
7 purchase totals =	$1,113.73		$1,209.5340	$1,209.53	$1,209.55	$1,209.50