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	$237.31	11.431%	$264.4369	$264.44	$264.45	$264.40
Purchase #2	$127.57	6.751%	$136.1823	$136.18	$136.20	$136.20
Purchase #3	$86.41	3.141%	$89.1241	$89.12	$89.10	$89.10
Purchase #4	$89.83	5.621%	$94.8793	$94.88	$94.90	$94.90
Purchase #5	$222.27	4.387%	$232.021	$232.02	$232.00	$232.00
Purchase #6	$222.33	13.287%	$251.871	$251.87	$251.85	$251.90
Purchase #7	$231.34	13.591%	$262.7814	$262.78	$262.80	$262.80
7 purchase totals =	$1,217.06		$1,331.2960	$1,331.29	$1,331.30	$1,331.30