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	$169.72	12.211%	$190.4445	$190.44	$190.45	$190.40
Purchase #2	$94.80	5.749%	$100.2501	$100.25	$100.25	$100.30
Purchase #3	$31.69	3.763%	$32.8825	$32.88	$32.90	$32.90
Purchase #4	$198.95	6.244%	$211.3724	$211.37	$211.35	$211.40
Purchase #5	$55.97	13.307%	$63.4179	$63.42	$63.40	$63.40
Purchase #6	$187.44	3.132%	$193.3106	$193.31	$193.30	$193.30
Purchase #7	$214.83	6.241%	$228.2375	$228.24	$228.25	$228.20
7 purchase totals =	$953.40		$1,019.9155	$1,019.91	$1,019.90	$1,019.90