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	$161.72	3.463%	$167.3204	$167.32	$167.30	$167.30
Purchase #2	$196.76	11.230%	$218.8561	$218.86	$218.85	$218.90
Purchase #3	$58.77	4.663%	$61.5104	$61.51	$61.50	$61.50
Purchase #4	$208.96	10.551%	$231.0074	$231.01	$231.00	$231.00
Purchase #5	$108.89	10.562%	$120.391	$120.39	$120.40	$120.40
Purchase #6	$175.73	12.718%	$198.0793	$198.08	$198.10	$198.10
Purchase #7	$182.38	9.536%	$199.7718	$199.77	$199.75	$199.80
7 purchase totals =	$1,093.21		$1,196.9364	$1,196.94	$1,196.90	$1,197.00