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	$222.68	5.764%	$235.5153	$235.52	$235.50	$235.50
Purchase #2	$72.31	5.333%	$76.1663	$76.17	$76.15	$76.20
Purchase #3	$19.25	13.842%	$21.9146	$21.91	$21.90	$21.90
Purchase #4	$198.72	3.392%	$205.4606	$205.46	$205.45	$205.50
Purchase #5	$201.34	10.521%	$222.523	$222.52	$222.50	$222.50
Purchase #6	$224.95	5.410%	$237.1198	$237.12	$237.10	$237.10
Purchase #7	$207.89	13.245%	$235.425	$235.43	$235.45	$235.40
7 purchase totals =	$1,147.14		$1,234.1246	$1,234.13	$1,234.05	$1,234.10