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	$136.76	10.403%	$150.9871	$150.99	$151.00	$151.00
Purchase #2	$79.83	3.781%	$82.8484	$82.85	$82.85	$82.80
Purchase #3	$91.41	10.315%	$100.8389	$100.84	$100.85	$100.80
Purchase #4	$77.78	12.444%	$87.4589	$87.46	$87.45	$87.50
Purchase #5	$62.98	5.668%	$66.5497	$66.55	$66.55	$66.50
Purchase #6	$228.32	7.111%	$244.5558	$244.56	$244.55	$244.60
Purchase #7	$241.29	9.316%	$263.7686	$263.77	$263.75	$263.80
7 purchase totals =	$918.37		$997.0074	$997.02	$997.00	$997.00