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	$41.71	9.873%	$45.828	$45.83	$45.85	$45.80
Purchase #2	$79.46	11.859%	$88.8832	$88.88	$88.90	$88.90
Purchase #3	$79.83	11.244%	$88.8061	$88.81	$88.80	$88.80
Purchase #4	$56.48	4.781%	$59.1803	$59.18	$59.20	$59.20
Purchase #5	$244.39	10.561%	$270.2	$270.20	$270.20	$270.20
Purchase #6	$31.92	4.872%	$33.4751	$33.48	$33.50	$33.50
Purchase #7	$59.60	6.850%	$63.6826	$63.68	$63.70	$63.70
7 purchase totals =	$593.39		$650.0553	$650.06	$650.15	$650.10