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	$32.72	10.743%	$36.2351	$36.24	$36.25	$36.20
Purchase #2	$148.48	11.657%	$165.7883	$165.79	$165.80	$165.80
Purchase #3	$127.94	11.698%	$142.9064	$142.91	$142.90	$142.90
Purchase #4	$171.52	12.247%	$192.5261	$192.53	$192.55	$192.50
Purchase #5	$144.52	12.869%	$163.1183	$163.12	$163.10	$163.10
Purchase #6	$105.48	6.107%	$111.9217	$111.92	$111.90	$111.90
Purchase #7	$81.39	12.658%	$91.6923	$91.69	$91.70	$91.70
7 purchase totals =	$812.05		$904.1882	$904.20	$904.20	$904.10