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	$208.97	4.496%	$218.3653	$218.37	$218.35	$218.40
Purchase #2	$152.33	11.270%	$169.4976	$169.50	$169.50	$169.50
Purchase #3	$159.94	4.640%	$167.3612	$167.36	$167.35	$167.40
Purchase #4	$96.58	9.599%	$105.8507	$105.85	$105.85	$105.90
Purchase #5	$221.78	10.793%	$245.7167	$245.72	$245.70	$245.70
Purchase #6	$62.37	8.764%	$67.8361	$67.84	$67.85	$67.80
Purchase #7	$169.55	7.770%	$182.724	$182.72	$182.70	$182.70
7 purchase totals =	$1,071.52		$1,157.3516	$1,157.36	$1,157.30	$1,157.40