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	$179.25	4.259%	$186.8843	$186.88	$186.90	$186.90
Purchase #2	$158.93	4.384%	$165.8975	$165.90	$165.90	$165.90
Purchase #3	$99.88	13.714%	$113.5775	$113.58	$113.60	$113.60
Purchase #4	$245.33	5.414%	$258.6122	$258.61	$258.60	$258.60
Purchase #5	$186.26	13.531%	$211.4628	$211.46	$211.45	$211.50
Purchase #6	$78.89	4.365%	$82.3335	$82.33	$82.35	$82.30
Purchase #7	$41.69	9.216%	$45.5322	$45.53	$45.55	$45.50
7 purchase totals =	$990.23		$1,064.3000	$1,064.29	$1,064.35	$1,064.30