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	$216.43	3.423%	$223.8384	$223.84	$223.85	$223.80
Purchase #2	$121.96	5.575%	$128.7593	$128.76	$128.75	$128.80
Purchase #3	$245.38	7.769%	$264.4436	$264.44	$264.45	$264.40
Purchase #4	$191.42	6.229%	$203.3436	$203.34	$203.35	$203.30
Purchase #5	$56.64	9.165%	$61.8311	$61.83	$61.85	$61.80
Purchase #6	$189.39	11.148%	$210.5032	$210.50	$210.50	$210.50
Purchase #7	$139.90	13.529%	$158.8271	$158.83	$158.85	$158.80
7 purchase totals =	$1,161.12		$1,251.5463	$1,251.54	$1,251.60	$1,251.40