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	$229.50	8.254%	$248.4429	$248.44	$248.45	$248.40
Purchase #2	$57.61	13.440%	$65.3528	$65.35	$65.35	$65.40
Purchase #3	$98.60	7.361%	$105.8579	$105.86	$105.85	$105.90
Purchase #4	$63.56	7.672%	$68.4363	$68.44	$68.45	$68.40
Purchase #5	$189.91	3.481%	$196.5208	$196.52	$196.50	$196.50
Purchase #6	$225.28	6.634%	$240.2251	$240.23	$240.25	$240.20
Purchase #7	$154.28	11.396%	$171.8617	$171.86	$171.85	$171.90
7 purchase totals =	$1,018.74		$1,096.6975	$1,096.70	$1,096.70	$1,096.70