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	$171.33	4.541%	$179.1101	$179.11	$179.10	$179.10
Purchase #2	$62.35	6.718%	$66.5387	$66.54	$66.55	$66.50
Purchase #3	$237.83	9.449%	$260.3026	$260.30	$260.30	$260.30
Purchase #4	$29.38	6.509%	$31.2923	$31.29	$31.30	$31.30
Purchase #5	$67.87	4.864%	$71.1712	$71.17	$71.15	$71.20
Purchase #6	$216.33	4.423%	$225.8983	$225.90	$225.90	$225.90
Purchase #7	$206.58	13.399%	$234.2597	$234.26	$234.25	$234.30
7 purchase totals =	$991.67		$1,068.5729	$1,068.57	$1,068.55	$1,068.60