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	$242.63	12.285%	$272.4371	$272.44	$272.45	$272.40
Purchase #2	$195.50	11.785%	$218.5397	$218.54	$218.55	$218.50
Purchase #3	$81.56	5.240%	$85.8337	$85.83	$85.85	$85.80
Purchase #4	$180.66	6.143%	$191.7579	$191.76	$191.75	$191.80
Purchase #5	$94.41	11.817%	$105.5664	$105.57	$105.55	$105.60
Purchase #6	$196.78	13.478%	$223.302	$223.30	$223.30	$223.30
Purchase #7	$184.86	12.870%	$208.6515	$208.65	$208.65	$208.70
7 purchase totals =	$1,176.40		$1,306.0883	$1,306.09	$1,306.10	$1,306.10