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	$159.65	5.645%	$168.6622	$168.66	$168.65	$168.70
Purchase #2	$212.51	8.175%	$229.8827	$229.88	$229.90	$229.90
Purchase #3	$127.52	5.665%	$134.744	$134.74	$134.75	$134.70
Purchase #4	$225.45	10.646%	$249.4514	$249.45	$249.45	$249.50
Purchase #5	$86.88	5.330%	$91.5107	$91.51	$91.50	$91.50
Purchase #6	$31.55	5.483%	$33.2799	$33.28	$33.30	$33.30
Purchase #7	$238.56	11.647%	$266.3451	$266.35	$266.35	$266.30
7 purchase totals =	$1,082.12		$1,173.8760	$1,173.87	$1,173.90	$1,173.90