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	$55.73	10.780%	$61.7377	$61.74	$61.75	$61.70
Purchase #2	$111.69	10.374%	$123.2767	$123.28	$123.30	$123.30
Purchase #3	$157.31	11.868%	$175.9796	$175.98	$176.00	$176.00
Purchase #4	$218.41	3.631%	$226.3405	$226.34	$226.35	$226.30
Purchase #5	$75.43	4.453%	$78.7889	$78.79	$78.80	$78.80
Purchase #6	$103.91	9.188%	$113.4573	$113.46	$113.45	$113.50
Purchase #7	$9.98	13.619%	$11.3392	$11.34	$11.35	$11.30
7 purchase totals =	$732.46		$790.9199	$790.93	$791.00	$790.90