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	$189.90	9.506%	$207.9519	$207.95	$207.95	$208.00
Purchase #2	$179.91	6.512%	$191.6257	$191.63	$191.65	$191.60
Purchase #3	$86.72	3.126%	$89.4309	$89.43	$89.45	$89.40
Purchase #4	$58.99	11.429%	$65.732	$65.73	$65.75	$65.70
Purchase #5	$93.54	13.173%	$105.862	$105.86	$105.85	$105.90
Purchase #6	$78.45	6.183%	$83.3006	$83.30	$83.30	$83.30
Purchase #7	$130.89	12.824%	$147.6753	$147.68	$147.70	$147.70
7 purchase totals =	$818.40		$891.5784	$891.58	$891.65	$891.60