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	$184.35	6.715%	$196.7291	$196.73	$196.75	$196.70
Purchase #2	$36.54	8.537%	$39.6594	$39.66	$39.65	$39.70
Purchase #3	$98.36	12.150%	$110.3107	$110.31	$110.30	$110.30
Purchase #4	$100.33	9.485%	$109.8463	$109.85	$109.85	$109.80
Purchase #5	$200.48	7.732%	$215.9811	$215.98	$216.00	$216.00
Purchase #6	$90.61	4.873%	$95.0254	$95.03	$95.05	$95.00
Purchase #7	$105.35	12.490%	$118.5082	$118.51	$118.50	$118.50
7 purchase totals =	$816.02		$886.0602	$886.07	$886.10	$886.00