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	$166.89	4.120%	$173.7659	$173.77	$173.75	$173.80
Purchase #2	$9.96	6.489%	$10.6063	$10.61	$10.60	$10.60
Purchase #3	$166.37	12.180%	$186.6339	$186.63	$186.65	$186.60
Purchase #4	$196.76	10.149%	$216.7292	$216.73	$216.75	$216.70
Purchase #5	$18.70	12.674%	$21.07	$21.07	$21.05	$21.10
Purchase #6	$144.75	6.545%	$154.2239	$154.22	$154.20	$154.20
Purchase #7	$241.53	4.859%	$253.2659	$253.27	$253.25	$253.30
7 purchase totals =	$944.96		$1,016.2951	$1,016.30	$1,016.25	$1,016.30