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	$61.50	4.782%	$64.4409	$64.44	$64.45	$64.40
Purchase #2	$56.45	6.470%	$60.1023	$60.10	$60.10	$60.10
Purchase #3	$64.73	10.631%	$71.6114	$71.61	$71.60	$71.60
Purchase #4	$170.95	5.566%	$180.4651	$180.47	$180.45	$180.50
Purchase #5	$83.46	8.140%	$90.2536	$90.25	$90.25	$90.30
Purchase #6	$224.58	8.330%	$243.2875	$243.29	$243.30	$243.30
Purchase #7	$250.79	11.336%	$279.2196	$279.22	$279.20	$279.20
7 purchase totals =	$912.46		$989.3804	$989.38	$989.35	$989.40