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	$198.50	6.203%	$210.813	$210.81	$210.80	$210.80
Purchase #2	$105.37	6.814%	$112.5499	$112.55	$112.55	$112.50
Purchase #3	$59.33	13.457%	$67.314	$67.31	$67.30	$67.30
Purchase #4	$43.64	6.218%	$46.3535	$46.35	$46.35	$46.40
Purchase #5	$32.51	13.149%	$36.7847	$36.78	$36.80	$36.80
Purchase #6	$96.53	5.769%	$102.0988	$102.10	$102.10	$102.10
Purchase #7	$238.90	8.273%	$258.6642	$258.66	$258.65	$258.70
7 purchase totals =	$774.78		$834.5781	$834.56	$834.55	$834.60