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	$221.75	6.135%	$235.3544	$235.35	$235.35	$235.40
Purchase #2	$85.85	8.588%	$93.2228	$93.22	$93.20	$93.20
Purchase #3	$189.44	3.870%	$196.7713	$196.77	$196.75	$196.80
Purchase #4	$154.32	9.217%	$168.5437	$168.54	$168.55	$168.50
Purchase #5	$96.83	6.865%	$103.4774	$103.48	$103.50	$103.50
Purchase #6	$234.98	5.559%	$248.0425	$248.04	$248.05	$248.00
Purchase #7	$68.51	13.858%	$78.0041	$78.00	$78.00	$78.00
7 purchase totals =	$1,051.68		$1,123.4162	$1,123.40	$1,123.40	$1,123.40