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	$223.87	9.622%	$245.4108	$245.41	$245.40	$245.40
Purchase #2	$89.93	4.436%	$93.9193	$93.92	$93.90	$93.90
Purchase #3	$115.69	6.754%	$123.5037	$123.50	$123.50	$123.50
Purchase #4	$247.90	7.204%	$265.7587	$265.76	$265.75	$265.80
Purchase #5	$163.66	7.124%	$175.3191	$175.32	$175.30	$175.30
Purchase #6	$126.48	6.205%	$134.3281	$134.33	$134.35	$134.30
Purchase #7	$38.39	9.629%	$42.0866	$42.09	$42.10	$42.10
7 purchase totals =	$1,005.92		$1,080.3263	$1,080.33	$1,080.30	$1,080.30