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	$92.38	9.846%	$101.4757	$101.48	$101.50	$101.50
Purchase #2	$246.42	11.843%	$275.6035	$275.60	$275.60	$275.60
Purchase #3	$41.62	4.534%	$43.5071	$43.51	$43.50	$43.50
Purchase #4	$47.45	7.130%	$50.8332	$50.83	$50.85	$50.80
Purchase #5	$135.62	7.317%	$145.5433	$145.54	$145.55	$145.50
Purchase #6	$148.74	3.174%	$153.461	$153.46	$153.45	$153.50
Purchase #7	$196.87	7.872%	$212.3676	$212.37	$212.35	$212.40
7 purchase totals =	$909.10		$982.7914	$982.79	$982.80	$982.80