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	$113.38	3.581%	$117.4401	$117.44	$117.45	$117.40
Purchase #2	$18.26	9.631%	$20.0186	$20.02	$20.00	$20.00
Purchase #3	$207.46	10.530%	$229.3055	$229.31	$229.30	$229.30
Purchase #4	$40.62	11.631%	$45.3445	$45.34	$45.35	$45.30
Purchase #5	$85.99	9.348%	$94.0283	$94.03	$94.05	$94.00
Purchase #6	$77.27	13.137%	$87.421	$87.42	$87.40	$87.40
Purchase #7	$72.80	7.256%	$78.0824	$78.08	$78.10	$78.10
7 purchase totals =	$615.78		$671.6404	$671.64	$671.65	$671.50