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	$217.91	5.121%	$229.0692	$229.07	$229.05	$229.10
Purchase #2	$82.61	4.647%	$86.4489	$86.45	$86.45	$86.40
Purchase #3	$92.42	5.159%	$97.1879	$97.19	$97.20	$97.20
Purchase #4	$33.56	6.669%	$35.7981	$35.80	$35.80	$35.80
Purchase #5	$55.74	6.794%	$59.527	$59.53	$59.55	$59.50
Purchase #6	$130.77	7.799%	$140.9688	$140.97	$140.95	$141.00
Purchase #7	$16.51	12.384%	$18.5546	$18.55	$18.55	$18.60
7 purchase totals =	$629.52		$667.5545	$667.56	$667.55	$667.60