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	$61.87	9.532%	$67.7674	$67.77	$67.75	$67.80
Purchase #2	$27.85	11.820%	$31.1419	$31.14	$31.15	$31.10
Purchase #3	$215.44	5.662%	$227.6382	$227.64	$227.65	$227.60
Purchase #4	$168.53	10.266%	$185.8313	$185.83	$185.85	$185.80
Purchase #5	$193.87	11.773%	$216.6943	$216.69	$216.70	$216.70
Purchase #6	$195.71	13.465%	$222.0624	$222.06	$222.05	$222.10
Purchase #7	$226.68	5.256%	$238.5943	$238.59	$238.60	$238.60
7 purchase totals =	$1,089.95		$1,189.7298	$1,189.72	$1,189.75	$1,189.70