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	$168.29	12.396%	$189.1512	$189.15	$189.15	$189.20
Purchase #2	$7.58	10.139%	$8.3485	$8.35	$8.35	$8.30
Purchase #3	$126.62	10.628%	$140.0772	$140.08	$140.10	$140.10
Purchase #4	$126.30	12.764%	$142.4209	$142.42	$142.40	$142.40
Purchase #5	$227.30	10.293%	$250.696	$250.70	$250.70	$250.70
Purchase #6	$157.77	6.256%	$167.6401	$167.64	$167.65	$167.60
Purchase #7	$89.45	10.851%	$99.1562	$99.16	$99.15	$99.20
7 purchase totals =	$903.31		$997.4901	$997.50	$997.50	$997.50