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	$152.64	13.272%	$172.8984	$172.90	$172.90	$172.90
Purchase #2	$221.26	5.367%	$233.135	$233.14	$233.15	$233.10
Purchase #3	$228.69	11.852%	$255.7943	$255.79	$255.80	$255.80
Purchase #4	$215.87	8.482%	$234.1801	$234.18	$234.20	$234.20
Purchase #5	$111.71	10.497%	$123.4362	$123.44	$123.45	$123.40
Purchase #6	$36.44	6.416%	$38.778	$38.78	$38.80	$38.80
Purchase #7	$141.54	6.364%	$150.5476	$150.55	$150.55	$150.50
7 purchase totals =	$1,108.15		$1,208.7696	$1,208.78	$1,208.85	$1,208.70