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	$178.82	12.102%	$200.4608	$200.46	$200.45	$200.50
Purchase #2	$78.89	5.355%	$83.1146	$83.11	$83.10	$83.10
Purchase #3	$56.62	3.481%	$58.5909	$58.59	$58.60	$58.60
Purchase #4	$6.32	13.390%	$7.1662	$7.17	$7.15	$7.20
Purchase #5	$166.43	9.132%	$181.6284	$181.63	$181.65	$181.60
Purchase #6	$196.93	3.830%	$204.4724	$204.47	$204.45	$204.50
Purchase #7	$237.99	11.231%	$264.7187	$264.72	$264.70	$264.70
7 purchase totals =	$922.00		$1,000.1520	$1,000.15	$1,000.10	$1,000.20