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	$92.69	8.144%	$100.2387	$100.24	$100.25	$100.20
Purchase #2	$45.83	12.263%	$51.4501	$51.45	$51.45	$51.50
Purchase #3	$34.81	6.839%	$37.1907	$37.19	$37.20	$37.20
Purchase #4	$246.62	3.568%	$255.4194	$255.42	$255.40	$255.40
Purchase #5	$180.25	5.304%	$189.8105	$189.81	$189.80	$189.80
Purchase #6	$99.78	10.220%	$109.9775	$109.98	$110.00	$110.00
Purchase #7	$153.27	9.867%	$168.3932	$168.39	$168.40	$168.40
7 purchase totals =	$853.25		$912.4801	$912.48	$912.50	$912.50