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	$217.94	7.320%	$233.8932	$233.89	$233.90	$233.90
Purchase #2	$175.99	5.438%	$185.5603	$185.56	$185.55	$185.60
Purchase #3	$163.41	5.707%	$172.7358	$172.74	$172.75	$172.70
Purchase #4	$60.33	7.595%	$64.9121	$64.91	$64.90	$64.90
Purchase #5	$73.78	9.164%	$80.5412	$80.54	$80.55	$80.50
Purchase #6	$96.95	12.183%	$108.7614	$108.76	$108.75	$108.80
Purchase #7	$241.25	10.396%	$266.3304	$266.33	$266.35	$266.30
7 purchase totals =	$1,029.65		$1,112.7344	$1,112.73	$1,112.75	$1,112.70