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	$226.48	10.189%	$249.556	$249.56	$249.55	$249.60
Purchase #2	$43.82	11.171%	$48.7151	$48.72	$48.70	$48.70
Purchase #3	$229.42	6.531%	$244.4034	$244.40	$244.40	$244.40
Purchase #4	$36.25	3.624%	$37.5637	$37.56	$37.55	$37.60
Purchase #5	$180.78	4.637%	$189.1628	$189.16	$189.15	$189.20
Purchase #6	$88.65	3.173%	$91.4629	$91.46	$91.45	$91.50
Purchase #7	$155.54	4.732%	$162.9002	$162.90	$162.90	$162.90
7 purchase totals =	$960.94		$1,023.7641	$1,023.76	$1,023.70	$1,023.90