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	$134.27	11.142%	$149.2304	$149.23	$149.25	$149.20
Purchase #2	$195.45	13.615%	$222.0605	$222.06	$222.05	$222.10
Purchase #3	$12.46	13.756%	$14.174	$14.17	$14.15	$14.20
Purchase #4	$110.61	8.326%	$119.8194	$119.82	$119.80	$119.80
Purchase #5	$31.89	3.543%	$33.0199	$33.02	$33.00	$33.00
Purchase #6	$115.88	6.293%	$123.1723	$123.17	$123.15	$123.20
Purchase #7	$73.81	12.276%	$82.8709	$82.87	$82.85	$82.90
7 purchase totals =	$674.37		$744.3474	$744.34	$744.25	$744.40