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	$221.56	10.482%	$244.7839	$244.78	$244.80	$244.80
Purchase #2	$38.78	7.475%	$41.6788	$41.68	$41.70	$41.70
Purchase #3	$94.50	7.278%	$101.3777	$101.38	$101.40	$101.40
Purchase #4	$223.58	3.799%	$232.0738	$232.07	$232.05	$232.10
Purchase #5	$223.51	9.453%	$244.6384	$244.64	$244.65	$244.60
Purchase #6	$43.29	7.174%	$46.3956	$46.40	$46.40	$46.40
Purchase #7	$81.66	10.134%	$89.9354	$89.94	$89.95	$89.90
7 purchase totals =	$926.88		$1,000.8836	$1,000.89	$1,000.95	$1,000.90