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	$49.93	6.645%	$53.2478	$53.25	$53.25	$53.20
Purchase #2	$120.78	4.718%	$126.4784	$126.48	$126.50	$126.50
Purchase #3	$204.64	9.263%	$223.5958	$223.60	$223.60	$223.60
Purchase #4	$25.50	11.699%	$28.4832	$28.48	$28.50	$28.50
Purchase #5	$74.46	10.306%	$82.1338	$82.13	$82.15	$82.10
Purchase #6	$243.52	4.436%	$254.3225	$254.32	$254.30	$254.30
Purchase #7	$101.85	7.129%	$109.1109	$109.11	$109.10	$109.10
7 purchase totals =	$820.68		$877.3724	$877.37	$877.40	$877.30