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	$181.35	8.483%	$196.7339	$196.73	$196.75	$196.70
Purchase #2	$59.32	6.537%	$63.1977	$63.20	$63.20	$63.20
Purchase #3	$98.48	13.673%	$111.9452	$111.95	$111.95	$111.90
Purchase #4	$69.73	3.414%	$72.1106	$72.11	$72.10	$72.10
Purchase #5	$189.34	12.501%	$213.0094	$213.01	$213.00	$213.00
Purchase #6	$162.36	4.237%	$169.2392	$169.24	$169.25	$169.20
Purchase #7	$173.46	3.656%	$179.8017	$179.80	$179.80	$179.80
7 purchase totals =	$934.04		$1,006.0377	$1,006.04	$1,006.05	$1,005.90