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	$209.33	4.129%	$217.9732	$217.97	$217.95	$218.00
Purchase #2	$232.36	8.595%	$252.3313	$252.33	$252.35	$252.30
Purchase #3	$47.42	11.660%	$52.9492	$52.95	$52.95	$52.90
Purchase #4	$145.32	4.284%	$151.5455	$151.55	$151.55	$151.50
Purchase #5	$211.86	5.315%	$223.1204	$223.12	$223.10	$223.10
Purchase #6	$83.38	7.608%	$89.7236	$89.72	$89.70	$89.70
Purchase #7	$244.69	4.785%	$256.3984	$256.40	$256.40	$256.40
7 purchase totals =	$1,174.36		$1,244.0416	$1,244.04	$1,244.00	$1,243.90