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	$84.59	8.572%	$91.8411	$91.84	$91.85	$91.80
Purchase #2	$160.71	3.359%	$166.1082	$166.11	$166.10	$166.10
Purchase #3	$48.74	8.746%	$53.0028	$53.00	$53.00	$53.00
Purchase #4	$191.51	7.331%	$205.5496	$205.55	$205.55	$205.50
Purchase #5	$160.30	13.360%	$181.7161	$181.72	$181.70	$181.70
Purchase #6	$208.45	9.168%	$227.5607	$227.56	$227.55	$227.60
Purchase #7	$146.83	9.440%	$160.6908	$160.69	$160.70	$160.70
7 purchase totals =	$1,001.13		$1,086.4693	$1,086.47	$1,086.45	$1,086.40