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	$180.91	9.192%	$197.5392	$197.54	$197.55	$197.50
Purchase #2	$122.58	12.514%	$137.9197	$137.92	$137.90	$137.90
Purchase #3	$90.91	8.352%	$98.5028	$98.50	$98.50	$98.50
Purchase #4	$115.40	13.333%	$130.7863	$130.79	$130.80	$130.80
Purchase #5	$242.88	3.607%	$251.6407	$251.64	$251.65	$251.60
Purchase #6	$109.67	3.455%	$113.4591	$113.46	$113.45	$113.50
Purchase #7	$240.56	10.864%	$266.6944	$266.69	$266.70	$266.70
7 purchase totals =	$1,102.91		$1,196.5422	$1,196.54	$1,196.55	$1,196.50