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	$80.32	7.586%	$86.4131	$86.41	$86.40	$86.40
Purchase #2	$37.30	9.486%	$40.8383	$40.84	$40.85	$40.80
Purchase #3	$152.96	3.663%	$158.5629	$158.56	$158.55	$158.60
Purchase #4	$43.58	7.650%	$46.9139	$46.91	$46.90	$46.90
Purchase #5	$199.37	6.134%	$211.5994	$211.60	$211.60	$211.60
Purchase #6	$34.57	11.706%	$38.6168	$38.62	$38.60	$38.60
Purchase #7	$231.58	5.114%	$243.423	$243.42	$243.40	$243.40
7 purchase totals =	$779.68		$826.3674	$826.36	$826.30	$826.30