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	$209.67	8.467%	$227.4228	$227.42	$227.40	$227.40
Purchase #2	$225.52	11.372%	$251.1661	$251.17	$251.15	$251.20
Purchase #3	$240.53	4.143%	$250.4952	$250.50	$250.50	$250.50
Purchase #4	$195.94	6.140%	$207.9707	$207.97	$207.95	$208.00
Purchase #5	$86.51	3.562%	$89.5915	$89.59	$89.60	$89.60
Purchase #6	$57.37	3.142%	$59.1726	$59.17	$59.15	$59.20
Purchase #7	$91.58	8.310%	$99.1903	$99.19	$99.20	$99.20
7 purchase totals =	$1,107.12		$1,185.0092	$1,185.01	$1,184.95	$1,185.10