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	$103.78	11.307%	$115.5144	$115.51	$115.50	$115.50
Purchase #2	$155.53	5.686%	$164.3734	$164.37	$164.35	$164.40
Purchase #3	$219.52	6.307%	$233.3651	$233.37	$233.35	$233.40
Purchase #4	$164.89	12.401%	$185.338	$185.34	$185.35	$185.30
Purchase #5	$250.77	5.499%	$264.5598	$264.56	$264.55	$264.60
Purchase #6	$7.44	7.717%	$8.0141	$8.01	$8.00	$8.00
Purchase #7	$78.27	7.291%	$83.9767	$83.98	$84.00	$84.00
7 purchase totals =	$980.20		$1,055.1415	$1,055.14	$1,055.10	$1,055.20