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	$156.51	7.142%	$167.6879	$167.69	$167.70	$167.70
Purchase #2	$43.95	3.617%	$45.5397	$45.54	$45.55	$45.50
Purchase #3	$72.31	11.366%	$80.5288	$80.53	$80.55	$80.50
Purchase #4	$115.29	4.289%	$120.2348	$120.23	$120.25	$120.20
Purchase #5	$220.83	4.565%	$230.9109	$230.91	$230.90	$230.90
Purchase #6	$243.96	12.650%	$274.8209	$274.82	$274.80	$274.80
Purchase #7	$138.32	8.314%	$149.8199	$149.82	$149.80	$149.80
7 purchase totals =	$991.17		$1,069.5429	$1,069.54	$1,069.55	$1,069.40