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	$104.56	11.287%	$116.3617	$116.36	$116.35	$116.40
Purchase #2	$119.97	13.292%	$135.9164	$135.92	$135.90	$135.90
Purchase #3	$35.89	3.339%	$37.0884	$37.09	$37.10	$37.10
Purchase #4	$163.78	13.210%	$185.4153	$185.42	$185.40	$185.40
Purchase #5	$148.88	6.859%	$159.0917	$159.09	$159.10	$159.10
Purchase #6	$84.36	6.353%	$89.7194	$89.72	$89.70	$89.70
Purchase #7	$64.85	11.186%	$72.1041	$72.10	$72.10	$72.10
7 purchase totals =	$722.29		$795.6970	$795.70	$795.65	$795.70