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	$13.52	11.264%	$15.0429	$15.04	$15.05	$15.00
Purchase #2	$31.91	9.851%	$35.0535	$35.05	$35.05	$35.10
Purchase #3	$69.72	10.258%	$76.8719	$76.87	$76.85	$76.90
Purchase #4	$88.44	4.377%	$92.311	$92.31	$92.30	$92.30
Purchase #5	$52.46	6.143%	$55.6826	$55.68	$55.70	$55.70
Purchase #6	$52.62	13.625%	$59.7895	$59.79	$59.80	$59.80
Purchase #7	$106.34	5.720%	$112.4226	$112.42	$112.40	$112.40
7 purchase totals =	$415.01		$447.1740	$447.16	$447.15	$447.20