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	$180.36	4.304%	$188.1227	$188.12	$188.10	$188.10
Purchase #2	$64.36	4.690%	$67.3785	$67.38	$67.40	$67.40
Purchase #3	$99.29	5.709%	$104.9585	$104.96	$104.95	$105.00
Purchase #4	$88.60	10.245%	$97.6771	$97.68	$97.70	$97.70
Purchase #5	$134.69	7.667%	$145.0167	$145.02	$145.00	$145.00
Purchase #6	$7.49	4.311%	$7.8129	$7.81	$7.80	$7.80
Purchase #7	$136.49	13.812%	$155.342	$155.34	$155.35	$155.30
7 purchase totals =	$711.28		$766.3084	$766.31	$766.30	$766.30