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	$221.40	9.546%	$242.5348	$242.53	$242.55	$242.50
Purchase #2	$47.82	9.221%	$52.2295	$52.23	$52.25	$52.20
Purchase #3	$210.89	11.630%	$235.4165	$235.42	$235.40	$235.40
Purchase #4	$110.48	10.339%	$121.9025	$121.90	$121.90	$121.90
Purchase #5	$141.77	10.666%	$156.8912	$156.89	$156.90	$156.90
Purchase #6	$36.61	5.803%	$38.7345	$38.73	$38.75	$38.70
Purchase #7	$158.89	6.551%	$169.2989	$169.30	$169.30	$169.30
7 purchase totals =	$927.86		$1,017.0079	$1,017.00	$1,017.05	$1,016.90