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	$65.35	3.579%	$67.6889	$67.69	$67.70	$67.70
Purchase #2	$51.81	3.740%	$53.7477	$53.75	$53.75	$53.70
Purchase #3	$70.50	12.135%	$79.0552	$79.06	$79.05	$79.10
Purchase #4	$208.37	12.276%	$233.9495	$233.95	$233.95	$233.90
Purchase #5	$205.78	13.788%	$234.1529	$234.15	$234.15	$234.20
Purchase #6	$24.38	12.422%	$27.4085	$27.41	$27.40	$27.40
Purchase #7	$240.38	6.465%	$255.9206	$255.92	$255.90	$255.90
7 purchase totals =	$866.57		$951.9233	$951.93	$951.90	$951.90