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	$152.85	7.846%	$164.8426	$164.84	$164.85	$164.80
Purchase #2	$21.89	7.583%	$23.5499	$23.55	$23.55	$23.50
Purchase #3	$188.69	6.244%	$200.4718	$200.47	$200.45	$200.50
Purchase #4	$96.51	3.571%	$99.9564	$99.96	$99.95	$100.00
Purchase #5	$211.74	12.843%	$238.9338	$238.93	$238.95	$238.90
Purchase #6	$25.39	11.207%	$28.2355	$28.24	$28.25	$28.20
Purchase #7	$7.53	10.622%	$8.3298	$8.33	$8.35	$8.30
7 purchase totals =	$704.60		$764.3198	$764.32	$764.35	$764.20