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	$95.78	8.715%	$104.1272	$104.13	$104.15	$104.10
Purchase #2	$240.44	11.435%	$267.9343	$267.93	$267.95	$267.90
Purchase #3	$56.76	13.410%	$64.3715	$64.37	$64.35	$64.40
Purchase #4	$116.98	8.608%	$127.0496	$127.05	$127.05	$127.00
Purchase #5	$144.95	5.239%	$152.5439	$152.54	$152.55	$152.50
Purchase #6	$78.60	13.614%	$89.3006	$89.30	$89.30	$89.30
Purchase #7	$128.53	8.544%	$139.5116	$139.51	$139.50	$139.50
7 purchase totals =	$862.04		$944.8387	$944.83	$944.85	$944.70