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	$171.46	9.658%	$188.0196	$188.02	$188.00	$188.00
Purchase #2	$212.88	5.754%	$225.1291	$225.13	$225.15	$225.10
Purchase #3	$213.49	5.536%	$225.3088	$225.31	$225.30	$225.30
Purchase #4	$92.81	13.653%	$105.4813	$105.48	$105.50	$105.50
Purchase #5	$228.81	12.459%	$257.3174	$257.32	$257.30	$257.30
Purchase #6	$102.79	6.453%	$109.423	$109.42	$109.40	$109.40
Purchase #7	$51.67	7.500%	$55.5453	$55.55	$55.55	$55.50
7 purchase totals =	$1,073.91		$1,166.2245	$1,166.23	$1,166.20	$1,166.10