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	$198.34	6.331%	$210.8969	$210.90	$210.90	$210.90
Purchase #2	$175.52	11.185%	$195.1519	$195.15	$195.15	$195.20
Purchase #3	$249.45	9.624%	$273.4571	$273.46	$273.45	$273.50
Purchase #4	$211.38	10.339%	$233.2346	$233.23	$233.25	$233.20
Purchase #5	$37.75	13.259%	$42.7553	$42.76	$42.75	$42.80
Purchase #6	$168.77	7.846%	$182.0117	$182.01	$182.00	$182.00
Purchase #7	$94.69	11.771%	$105.836	$105.84	$105.85	$105.80
7 purchase totals =	$1,135.90		$1,243.3435	$1,243.35	$1,243.35	$1,243.40