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	$155.89	7.207%	$167.125	$167.13	$167.15	$167.10
Purchase #2	$74.63	6.438%	$79.4347	$79.43	$79.45	$79.40
Purchase #3	$94.53	10.598%	$104.5483	$104.55	$104.55	$104.50
Purchase #4	$82.51	12.374%	$92.7198	$92.72	$92.70	$92.70
Purchase #5	$13.87	12.562%	$15.6123	$15.61	$15.60	$15.60
Purchase #6	$115.67	6.694%	$123.4129	$123.41	$123.40	$123.40
Purchase #7	$68.78	13.782%	$78.2593	$78.26	$78.25	$78.30
7 purchase totals =	$605.88		$661.1123	$661.11	$661.10	$661.00