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	$133.55	3.292%	$137.9465	$137.95	$137.95	$137.90
Purchase #2	$38.69	4.254%	$40.3359	$40.34	$40.35	$40.30
Purchase #3	$165.27	5.310%	$174.0458	$174.05	$174.05	$174.00
Purchase #4	$140.54	4.820%	$147.314	$147.31	$147.30	$147.30
Purchase #5	$76.86	12.294%	$86.3092	$86.31	$86.30	$86.30
Purchase #6	$99.41	7.219%	$106.5864	$106.59	$106.60	$106.60
Purchase #7	$65.62	13.568%	$74.5233	$74.52	$74.50	$74.50
7 purchase totals =	$719.94		$767.0611	$767.07	$767.05	$766.90