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	$248.98	4.680%	$260.6323	$260.63	$260.65	$260.60
Purchase #2	$35.38	7.350%	$37.9804	$37.98	$38.00	$38.00
Purchase #3	$117.39	7.670%	$126.3938	$126.39	$126.40	$126.40
Purchase #4	$135.49	4.587%	$141.7049	$141.70	$141.70	$141.70
Purchase #5	$72.96	12.483%	$82.0676	$82.07	$82.05	$82.10
Purchase #6	$244.44	11.227%	$271.8833	$271.88	$271.90	$271.90
Purchase #7	$82.63	8.400%	$89.5709	$89.57	$89.55	$89.60
7 purchase totals =	$937.27		$1,010.2332	$1,010.22	$1,010.25	$1,010.30