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	$198.67	5.641%	$209.877	$209.88	$209.90	$209.90
Purchase #2	$200.72	4.631%	$210.0153	$210.02	$210.00	$210.00
Purchase #3	$240.37	11.512%	$268.0414	$268.04	$268.05	$268.00
Purchase #4	$10.78	7.639%	$11.6035	$11.60	$11.60	$11.60
Purchase #5	$21.91	11.496%	$24.4288	$24.43	$24.45	$24.40
Purchase #6	$231.34	5.349%	$243.7144	$243.71	$243.70	$243.70
Purchase #7	$105.40	11.321%	$117.3323	$117.33	$117.35	$117.30
7 purchase totals =	$1,009.19		$1,085.0127	$1,085.01	$1,085.05	$1,084.90