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	$102.29	9.218%	$111.7191	$111.72	$111.70	$111.70
Purchase #2	$227.58	7.726%	$245.1628	$245.16	$245.15	$245.20
Purchase #3	$85.63	11.228%	$95.2445	$95.24	$95.25	$95.20
Purchase #4	$97.60	6.835%	$104.271	$104.27	$104.25	$104.30
Purchase #5	$193.30	13.585%	$219.5598	$219.56	$219.55	$219.60
Purchase #6	$135.77	11.612%	$151.5356	$151.54	$151.55	$151.50
Purchase #7	$220.33	9.588%	$241.4552	$241.46	$241.45	$241.50
7 purchase totals =	$1,062.50		$1,168.9480	$1,168.95	$1,168.90	$1,169.00