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	$145.27	10.589%	$160.6526	$160.65	$160.65	$160.70
Purchase #2	$224.76	11.573%	$250.7715	$250.77	$250.75	$250.80
Purchase #3	$55.31	13.112%	$62.5622	$62.56	$62.55	$62.60
Purchase #4	$213.64	4.143%	$222.4911	$222.49	$222.50	$222.50
Purchase #5	$152.42	6.205%	$161.8777	$161.88	$161.90	$161.90
Purchase #6	$227.73	10.157%	$250.8605	$250.86	$250.85	$250.90
Purchase #7	$33.76	8.526%	$36.6384	$36.64	$36.65	$36.60
7 purchase totals =	$1,052.89		$1,145.8540	$1,145.85	$1,145.85	$1,146.00