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	$123.62	7.229%	$132.5565	$132.56	$132.55	$132.60
Purchase #2	$73.65	12.874%	$83.1317	$83.13	$83.15	$83.10
Purchase #3	$168.34	11.340%	$187.4298	$187.43	$187.45	$187.40
Purchase #4	$53.36	11.485%	$59.4884	$59.49	$59.50	$59.50
Purchase #5	$206.41	13.252%	$233.7635	$233.76	$233.75	$233.80
Purchase #6	$93.62	13.753%	$106.4956	$106.50	$106.50	$106.50
Purchase #7	$162.68	11.555%	$181.4777	$181.48	$181.50	$181.50
7 purchase totals =	$881.68		$984.3432	$984.35	$984.40	$984.40