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	$137.74	3.330%	$142.3267	$142.33	$142.35	$142.30
Purchase #2	$165.90	5.652%	$175.2767	$175.28	$175.30	$175.30
Purchase #3	$59.48	11.697%	$66.4374	$66.44	$66.45	$66.40
Purchase #4	$247.29	5.173%	$260.0823	$260.08	$260.10	$260.10
Purchase #5	$77.59	7.607%	$83.4923	$83.49	$83.50	$83.50
Purchase #6	$139.29	9.761%	$152.8861	$152.89	$152.90	$152.90
Purchase #7	$95.69	8.576%	$103.8964	$103.90	$103.90	$103.90
7 purchase totals =	$922.98		$984.3979	$984.41	$984.50	$984.40