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	$138.40	5.252%	$145.6688	$145.67	$145.65	$145.70
Purchase #2	$147.49	12.837%	$166.4233	$166.42	$166.40	$166.40
Purchase #3	$237.64	5.761%	$251.3304	$251.33	$251.35	$251.30
Purchase #4	$54.87	3.624%	$56.8585	$56.86	$56.85	$56.90
Purchase #5	$190.76	5.247%	$200.7692	$200.77	$200.75	$200.80
Purchase #6	$31.26	3.384%	$32.3178	$32.32	$32.30	$32.30
Purchase #7	$216.58	13.474%	$245.762	$245.76	$245.75	$245.80
7 purchase totals =	$1,017.00		$1,099.1300	$1,099.13	$1,099.05	$1,099.20