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	$151.54	8.487%	$164.4012	$164.40	$164.40	$164.40
Purchase #2	$219.62	4.322%	$229.112	$229.11	$229.10	$229.10
Purchase #3	$98.31	4.838%	$103.0662	$103.07	$103.05	$103.10
Purchase #4	$93.43	6.499%	$99.502	$99.50	$99.50	$99.50
Purchase #5	$47.34	8.604%	$51.4131	$51.41	$51.40	$51.40
Purchase #6	$136.44	12.366%	$153.3122	$153.31	$153.30	$153.30
Purchase #7	$135.57	12.667%	$152.7427	$152.74	$152.75	$152.70
7 purchase totals =	$882.25		$953.5494	$953.54	$953.50	$953.50