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	$185.95	7.588%	$200.0599	$200.06	$200.05	$200.10
Purchase #2	$98.83	6.287%	$105.0434	$105.04	$105.05	$105.00
Purchase #3	$139.94	10.346%	$154.4182	$154.42	$154.40	$154.40
Purchase #4	$80.44	11.755%	$89.8957	$89.90	$89.90	$89.90
Purchase #5	$239.77	11.406%	$267.1182	$267.12	$267.10	$267.10
Purchase #6	$128.28	12.562%	$144.3945	$144.39	$144.40	$144.40
Purchase #7	$149.76	12.513%	$168.4995	$168.50	$168.50	$168.50
7 purchase totals =	$1,022.97		$1,129.4294	$1,129.43	$1,129.40	$1,129.40