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	$216.78	4.139%	$225.7525	$225.75	$225.75	$225.80
Purchase #2	$89.83	13.122%	$101.6175	$101.62	$101.60	$101.60
Purchase #3	$172.95	10.625%	$191.3259	$191.33	$191.35	$191.30
Purchase #4	$241.27	4.359%	$251.787	$251.79	$251.80	$251.80
Purchase #5	$96.78	4.836%	$101.4603	$101.46	$101.45	$101.50
Purchase #6	$138.66	12.516%	$156.0147	$156.01	$156.00	$156.00
Purchase #7	$46.46	10.196%	$51.1971	$51.20	$51.20	$51.20
7 purchase totals =	$1,002.73		$1,079.1550	$1,079.16	$1,079.15	$1,079.20