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	$245.39	7.467%	$263.7133	$263.71	$263.70	$263.70
Purchase #2	$206.48	13.816%	$235.0073	$235.01	$235.00	$235.00
Purchase #3	$142.65	6.405%	$151.7867	$151.79	$151.80	$151.80
Purchase #4	$124.93	7.309%	$134.0611	$134.06	$134.05	$134.10
Purchase #5	$103.77	3.612%	$107.5182	$107.52	$107.50	$107.50
Purchase #6	$100.74	10.497%	$111.3147	$111.31	$111.30	$111.30
Purchase #7	$34.89	8.755%	$37.9446	$37.94	$37.95	$37.90
7 purchase totals =	$958.85		$1,041.3459	$1,041.34	$1,041.30	$1,041.30