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	$166.40	11.402%	$185.3729	$185.37	$185.35	$185.40
Purchase #2	$145.33	9.378%	$158.959	$158.96	$158.95	$159.00
Purchase #3	$199.40	11.491%	$222.3131	$222.31	$222.30	$222.30
Purchase #4	$49.50	4.185%	$51.5716	$51.57	$51.55	$51.60
Purchase #5	$68.58	7.723%	$73.8764	$73.88	$73.90	$73.90
Purchase #6	$202.65	3.152%	$209.0375	$209.04	$209.05	$209.00
Purchase #7	$153.91	3.532%	$159.3461	$159.35	$159.35	$159.30
7 purchase totals =	$985.77		$1,060.4766	$1,060.48	$1,060.45	$1,060.50