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	$83.83	6.640%	$89.3963	$89.40	$89.40	$89.40
Purchase #2	$154.42	13.303%	$174.9625	$174.96	$174.95	$175.00
Purchase #3	$169.80	6.700%	$181.1766	$181.18	$181.20	$181.20
Purchase #4	$155.64	7.106%	$166.6998	$166.70	$166.70	$166.70
Purchase #5	$99.89	6.717%	$106.5996	$106.60	$106.60	$106.60
Purchase #6	$228.50	7.158%	$244.856	$244.86	$244.85	$244.90
Purchase #7	$142.89	5.179%	$150.2903	$150.29	$150.30	$150.30
7 purchase totals =	$1,034.97		$1,113.9811	$1,113.99	$1,114.00	$1,114.10