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	$189.31	11.255%	$210.6168	$210.62	$210.60	$210.60
Purchase #2	$221.96	6.384%	$236.1299	$236.13	$236.15	$236.10
Purchase #3	$137.86	10.598%	$152.4704	$152.47	$152.45	$152.50
Purchase #4	$192.71	7.496%	$207.1555	$207.16	$207.15	$207.20
Purchase #5	$153.98	12.173%	$172.724	$172.72	$172.70	$172.70
Purchase #6	$110.53	11.690%	$123.451	$123.45	$123.45	$123.50
Purchase #7	$114.37	7.623%	$123.0884	$123.09	$123.10	$123.10
7 purchase totals =	$1,120.72		$1,225.6360	$1,225.64	$1,225.60	$1,225.70