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	$147.86	7.269%	$158.6079	$158.61	$158.60	$158.60
Purchase #2	$120.63	8.507%	$130.892	$130.89	$130.90	$130.90
Purchase #3	$98.39	10.375%	$108.598	$108.60	$108.60	$108.60
Purchase #4	$75.65	8.744%	$82.2648	$82.26	$82.25	$82.30
Purchase #5	$148.83	6.222%	$158.0902	$158.09	$158.10	$158.10
Purchase #6	$114.31	5.346%	$120.421	$120.42	$120.40	$120.40
Purchase #7	$193.42	12.739%	$218.0598	$218.06	$218.05	$218.10
7 purchase totals =	$899.09		$976.9337	$976.93	$976.90	$977.00