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	$80.94	10.561%	$89.4881	$89.49	$89.50	$89.50
Purchase #2	$200.63	11.318%	$223.3373	$223.34	$223.35	$223.30
Purchase #3	$64.26	13.621%	$73.0129	$73.01	$73.00	$73.00
Purchase #4	$247.29	8.481%	$268.2627	$268.26	$268.25	$268.30
Purchase #5	$55.43	7.594%	$59.6394	$59.64	$59.65	$59.60
Purchase #6	$164.72	4.193%	$171.6267	$171.63	$171.65	$171.60
Purchase #7	$205.69	8.478%	$223.1284	$223.13	$223.15	$223.10
7 purchase totals =	$1,018.96		$1,108.4955	$1,108.50	$1,108.55	$1,108.40