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	$93.88	7.314%	$100.7464	$100.75	$100.75	$100.70
Purchase #2	$142.38	7.821%	$153.5155	$153.52	$153.50	$153.50
Purchase #3	$163.80	9.506%	$179.3708	$179.37	$179.35	$179.40
Purchase #4	$131.42	12.598%	$147.9763	$147.98	$148.00	$148.00
Purchase #5	$104.46	10.556%	$115.4868	$115.49	$115.50	$115.50
Purchase #6	$157.26	10.726%	$174.1277	$174.13	$174.15	$174.10
Purchase #7	$65.97	8.452%	$71.5458	$71.55	$71.55	$71.50
7 purchase totals =	$859.17		$942.7693	$942.79	$942.80	$942.70