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	$202.66	10.239%	$223.4104	$223.41	$223.40	$223.40
Purchase #2	$180.86	7.556%	$194.5258	$194.53	$194.55	$194.50
Purchase #3	$184.96	8.314%	$200.3376	$200.34	$200.35	$200.30
Purchase #4	$80.66	9.516%	$88.3356	$88.34	$88.35	$88.30
Purchase #5	$157.38	11.329%	$175.2096	$175.21	$175.20	$175.20
Purchase #6	$167.53	7.129%	$179.4732	$179.47	$179.45	$179.50
Purchase #7	$85.32	6.446%	$90.8197	$90.82	$90.80	$90.80
7 purchase totals =	$1,059.37		$1,152.1119	$1,152.12	$1,152.10	$1,152.00