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	$171.54	8.113%	$185.457	$185.46	$185.45	$185.50
Purchase #2	$160.52	5.399%	$169.1865	$169.19	$169.20	$169.20
Purchase #3	$7.66	13.362%	$8.6835	$8.68	$8.70	$8.70
Purchase #4	$75.72	10.329%	$83.5411	$83.54	$83.55	$83.50
Purchase #5	$48.38	4.815%	$50.7095	$50.71	$50.70	$50.70
Purchase #6	$119.75	6.518%	$127.5553	$127.56	$127.55	$127.60
Purchase #7	$78.66	6.744%	$83.9648	$83.96	$83.95	$84.00
7 purchase totals =	$662.23		$709.0977	$709.10	$709.10	$709.20