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	$202.35	4.862%	$212.1883	$212.19	$212.20	$212.20
Purchase #2	$19.32	11.861%	$21.6115	$21.61	$21.60	$21.60
Purchase #3	$82.31	11.314%	$91.6226	$91.62	$91.60	$91.60
Purchase #4	$47.92	9.118%	$52.2893	$52.29	$52.30	$52.30
Purchase #5	$45.35	11.150%	$50.4065	$50.41	$50.40	$50.40
Purchase #6	$140.76	5.617%	$148.6665	$148.67	$148.65	$148.70
Purchase #7	$195.95	13.408%	$222.223	$222.22	$222.20	$222.20
7 purchase totals =	$733.96		$799.0077	$799.01	$798.95	$799.00