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	$188.32	10.169%	$207.4703	$207.47	$207.45	$207.50
Purchase #2	$171.55	9.749%	$188.2744	$188.27	$188.25	$188.30
Purchase #3	$101.31	3.234%	$104.5864	$104.59	$104.60	$104.60
Purchase #4	$185.40	13.852%	$211.0816	$211.08	$211.10	$211.10
Purchase #5	$144.30	9.596%	$158.147	$158.15	$158.15	$158.10
Purchase #6	$191.80	12.814%	$216.3773	$216.38	$216.40	$216.40
Purchase #7	$156.38	8.498%	$169.6692	$169.67	$169.65	$169.70
7 purchase totals =	$1,139.06		$1,255.6062	$1,255.61	$1,255.60	$1,255.70