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	$91.64	7.213%	$98.25	$98.25	$98.25	$98.30
Purchase #2	$241.49	8.656%	$262.3934	$262.39	$262.40	$262.40
Purchase #3	$102.45	4.692%	$107.257	$107.26	$107.25	$107.30
Purchase #4	$202.27	9.247%	$220.9739	$220.97	$220.95	$221.00
Purchase #5	$87.61	3.364%	$90.5572	$90.56	$90.55	$90.60
Purchase #6	$35.64	4.305%	$37.1743	$37.17	$37.15	$37.20
Purchase #7	$165.68	11.697%	$185.0596	$185.06	$185.05	$185.10
7 purchase totals =	$926.78		$1,001.6654	$1,001.66	$1,001.60	$1,001.90