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	$99.90	7.752%	$107.6442	$107.64	$107.65	$107.60
Purchase #2	$89.56	13.846%	$101.9605	$101.96	$101.95	$102.00
Purchase #3	$92.98	3.650%	$96.3738	$96.37	$96.35	$96.40
Purchase #4	$241.64	10.767%	$267.6574	$267.66	$267.65	$267.70
Purchase #5	$242.67	4.738%	$254.1677	$254.17	$254.15	$254.20
Purchase #6	$37.42	8.858%	$40.7347	$40.73	$40.75	$40.70
Purchase #7	$142.69	5.833%	$151.0131	$151.01	$151.00	$151.00
7 purchase totals =	$946.86		$1,019.5514	$1,019.54	$1,019.50	$1,019.60