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	$78.49	5.429%	$82.7512	$82.75	$82.75	$82.80
Purchase #2	$65.59	10.572%	$72.5242	$72.52	$72.50	$72.50
Purchase #3	$180.65	8.627%	$196.2347	$196.23	$196.25	$196.20
Purchase #4	$206.79	7.654%	$222.6177	$222.62	$222.60	$222.60
Purchase #5	$157.56	5.258%	$165.8445	$165.84	$165.85	$165.80
Purchase #6	$180.25	9.609%	$197.5702	$197.57	$197.55	$197.60
Purchase #7	$130.49	12.594%	$146.9239	$146.92	$146.90	$146.90
7 purchase totals =	$999.82		$1,084.4664	$1,084.45	$1,084.40	$1,084.40