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	$132.37	11.273%	$147.2921	$147.29	$147.30	$147.30
Purchase #2	$161.28	11.214%	$179.3659	$179.37	$179.35	$179.40
Purchase #3	$30.76	7.503%	$33.0679	$33.07	$33.05	$33.10
Purchase #4	$118.30	8.261%	$128.0728	$128.07	$128.05	$128.10
Purchase #5	$217.29	7.529%	$233.6498	$233.65	$233.65	$233.60
Purchase #6	$196.50	13.380%	$222.7917	$222.79	$222.80	$222.80
Purchase #7	$69.36	8.620%	$75.3388	$75.34	$75.35	$75.30
7 purchase totals =	$925.86		$1,019.5790	$1,019.58	$1,019.55	$1,019.60