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	$202.43	3.742%	$210.0049	$210.00	$210.00	$210.00
Purchase #2	$42.91	6.798%	$45.827	$45.83	$45.85	$45.80
Purchase #3	$118.57	10.192%	$130.6547	$130.65	$130.65	$130.70
Purchase #4	$246.72	12.747%	$278.1694	$278.17	$278.15	$278.20
Purchase #5	$77.75	10.323%	$85.7761	$85.78	$85.80	$85.80
Purchase #6	$176.74	13.166%	$200.0096	$200.01	$200.00	$200.00
Purchase #7	$69.80	3.743%	$72.4126	$72.41	$72.40	$72.40
7 purchase totals =	$934.92		$1,022.8543	$1,022.85	$1,022.85	$1,022.90