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	$181.69	10.442%	$200.6621	$200.66	$200.65	$200.70
Purchase #2	$158.44	10.154%	$174.528	$174.53	$174.55	$174.50
Purchase #3	$243.67	4.839%	$255.4612	$255.46	$255.45	$255.50
Purchase #4	$187.56	12.417%	$210.8493	$210.85	$210.85	$210.80
Purchase #5	$197.76	13.709%	$224.8709	$224.87	$224.85	$224.90
Purchase #6	$89.85	10.260%	$99.0686	$99.07	$99.05	$99.10
Purchase #7	$208.47	11.604%	$232.6609	$232.66	$232.65	$232.70
7 purchase totals =	$1,267.44		$1,398.1010	$1,398.10	$1,398.05	$1,398.20