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	$35.75	3.757%	$37.0931	$37.09	$37.10	$37.10
Purchase #2	$155.33	6.184%	$164.9356	$164.94	$164.95	$164.90
Purchase #3	$54.65	11.837%	$61.1189	$61.12	$61.10	$61.10
Purchase #4	$60.70	4.459%	$63.4066	$63.41	$63.40	$63.40
Purchase #5	$86.88	12.227%	$97.5028	$97.50	$97.50	$97.50
Purchase #6	$9.76	3.644%	$10.1157	$10.12	$10.10	$10.10
Purchase #7	$127.43	3.658%	$132.0914	$132.09	$132.10	$132.10
7 purchase totals =	$530.50		$566.2641	$566.27	$566.25	$566.20