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	$43.47	6.854%	$46.4494	$46.45	$46.45	$46.40
Purchase #2	$240.33	4.254%	$250.5536	$250.55	$250.55	$250.60
Purchase #3	$20.97	9.174%	$22.8938	$22.89	$22.90	$22.90
Purchase #4	$31.66	11.578%	$35.3256	$35.33	$35.35	$35.30
Purchase #5	$31.70	12.299%	$35.5988	$35.60	$35.60	$35.60
Purchase #6	$176.74	5.537%	$186.5261	$186.53	$186.55	$186.50
Purchase #7	$236.60	13.647%	$268.8888	$268.89	$268.90	$268.90
7 purchase totals =	$781.47		$846.2361	$846.24	$846.30	$846.20