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	$160.34	4.215%	$167.0983	$167.10	$167.10	$167.10
Purchase #2	$138.56	5.218%	$145.7901	$145.79	$145.80	$145.80
Purchase #3	$61.35	6.460%	$65.3132	$65.31	$65.30	$65.30
Purchase #4	$210.45	7.109%	$225.4109	$225.41	$225.40	$225.40
Purchase #5	$237.85	7.411%	$255.4771	$255.48	$255.50	$255.50
Purchase #6	$68.45	6.572%	$72.9485	$72.95	$72.95	$72.90
Purchase #7	$247.99	3.557%	$256.811	$256.81	$256.80	$256.80
7 purchase totals =	$1,124.99		$1,188.8491	$1,188.85	$1,188.85	$1,188.80