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	$231.51	3.732%	$240.15	$240.15	$240.15	$240.20
Purchase #2	$99.49	3.513%	$102.9851	$102.99	$103.00	$103.00
Purchase #3	$52.93	11.259%	$58.8894	$58.89	$58.90	$58.90
Purchase #4	$176.50	11.132%	$196.148	$196.15	$196.15	$196.10
Purchase #5	$92.56	8.249%	$100.1953	$100.20	$100.20	$100.20
Purchase #6	$76.95	7.653%	$82.839	$82.84	$82.85	$82.80
Purchase #7	$153.61	8.740%	$167.0355	$167.04	$167.05	$167.00
7 purchase totals =	$883.55		$948.2423	$948.26	$948.30	$948.20