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	$214.34	13.666%	$243.6317	$243.63	$243.65	$243.60
Purchase #2	$99.64	9.785%	$109.3898	$109.39	$109.40	$109.40
Purchase #3	$33.91	10.355%	$37.4214	$37.42	$37.40	$37.40
Purchase #4	$213.53	9.300%	$233.3883	$233.39	$233.40	$233.40
Purchase #5	$7.78	4.141%	$8.1022	$8.10	$8.10	$8.10
Purchase #6	$70.35	5.808%	$74.4359	$74.44	$74.45	$74.40
Purchase #7	$166.37	3.764%	$172.6322	$172.63	$172.65	$172.60
7 purchase totals =	$805.92		$879.0015	$879.00	$879.05	$878.90