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	$246.51	4.159%	$256.7624	$256.76	$256.75	$256.80
Purchase #2	$231.31	9.486%	$253.2521	$253.25	$253.25	$253.30
Purchase #3	$71.87	7.106%	$76.9771	$76.98	$77.00	$77.00
Purchase #4	$191.77	7.329%	$205.8248	$205.82	$205.80	$205.80
Purchase #5	$169.58	6.476%	$180.562	$180.56	$180.55	$180.60
Purchase #6	$53.90	5.672%	$56.9572	$56.96	$56.95	$57.00
Purchase #7	$89.83	9.693%	$98.5372	$98.54	$98.55	$98.50
7 purchase totals =	$1,054.77		$1,128.8728	$1,128.87	$1,128.85	$1,129.00