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	$181.89	6.433%	$193.591	$193.59	$193.60	$193.60
Purchase #2	$111.80	6.791%	$119.3923	$119.39	$119.40	$119.40
Purchase #3	$215.65	8.412%	$233.7905	$233.79	$233.80	$233.80
Purchase #4	$227.57	11.661%	$254.1069	$254.11	$254.10	$254.10
Purchase #5	$52.39	7.606%	$56.3748	$56.37	$56.35	$56.40
Purchase #6	$116.71	10.432%	$128.8852	$128.89	$128.90	$128.90
Purchase #7	$77.87	3.435%	$80.5448	$80.54	$80.55	$80.50
7 purchase totals =	$983.88		$1,066.6855	$1,066.68	$1,066.70	$1,066.70