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	$183.42	7.430%	$197.0481	$197.05	$197.05	$197.00
Purchase #2	$220.90	4.471%	$230.7764	$230.78	$230.80	$230.80
Purchase #3	$101.87	7.150%	$109.1537	$109.15	$109.15	$109.20
Purchase #4	$73.33	7.416%	$78.7682	$78.77	$78.75	$78.80
Purchase #5	$102.49	9.224%	$111.9437	$111.94	$111.95	$111.90
Purchase #6	$224.60	13.214%	$254.2786	$254.28	$254.30	$254.30
Purchase #7	$138.66	7.828%	$149.5143	$149.51	$149.50	$149.50
7 purchase totals =	$1,045.27		$1,131.4830	$1,131.48	$1,131.50	$1,131.50