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	$178.30	8.366%	$193.2166	$193.22	$193.20	$193.20
Purchase #2	$152.57	3.461%	$157.8504	$157.85	$157.85	$157.90
Purchase #3	$101.89	13.612%	$115.7593	$115.76	$115.75	$115.80
Purchase #4	$82.79	9.359%	$90.5383	$90.54	$90.55	$90.50
Purchase #5	$100.84	4.459%	$105.3365	$105.34	$105.35	$105.30
Purchase #6	$189.74	3.304%	$196.009	$196.01	$196.00	$196.00
Purchase #7	$60.84	6.593%	$64.8512	$64.85	$64.85	$64.90
7 purchase totals =	$866.97		$923.5613	$923.57	$923.55	$923.60