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	$205.35	3.400%	$212.3319	$212.33	$212.35	$212.30
Purchase #2	$82.87	3.178%	$85.5036	$85.50	$85.50	$85.50
Purchase #3	$148.47	12.623%	$167.2114	$167.21	$167.20	$167.20
Purchase #4	$177.29	4.831%	$185.8549	$185.85	$185.85	$185.90
Purchase #5	$147.25	7.393%	$158.1362	$158.14	$158.15	$158.10
Purchase #6	$43.91	12.161%	$49.2499	$49.25	$49.25	$49.20
Purchase #7	$54.89	4.608%	$57.4193	$57.42	$57.40	$57.40
7 purchase totals =	$860.03		$915.7072	$915.70	$915.70	$915.60