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	$168.56	9.726%	$184.9541	$184.95	$184.95	$185.00
Purchase #2	$221.92	9.654%	$243.3442	$243.34	$243.35	$243.30
Purchase #3	$212.37	12.110%	$238.088	$238.09	$238.10	$238.10
Purchase #4	$162.92	5.340%	$171.6199	$171.62	$171.60	$171.60
Purchase #5	$118.31	11.375%	$131.7678	$131.77	$131.75	$131.80
Purchase #6	$25.76	12.805%	$29.0586	$29.06	$29.05	$29.10
Purchase #7	$153.36	11.549%	$171.0715	$171.07	$171.05	$171.10
7 purchase totals =	$1,063.20		$1,169.9041	$1,169.90	$1,169.85	$1,170.00