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	$65.25	4.626%	$68.2685	$68.27	$68.25	$68.30
Purchase #2	$16.70	9.728%	$18.3246	$18.32	$18.30	$18.30
Purchase #3	$115.72	12.578%	$130.2753	$130.28	$130.30	$130.30
Purchase #4	$143.76	4.321%	$149.9719	$149.97	$149.95	$150.00
Purchase #5	$130.37	10.809%	$144.4617	$144.46	$144.45	$144.50
Purchase #6	$59.84	10.131%	$65.9024	$65.90	$65.90	$65.90
Purchase #7	$171.30	6.784%	$182.921	$182.92	$182.90	$182.90
7 purchase totals =	$702.94		$760.1254	$760.12	$760.05	$760.20