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	$232.39	12.716%	$261.9407	$261.94	$261.95	$261.90
Purchase #2	$31.37	4.140%	$32.6687	$32.67	$32.65	$32.70
Purchase #3	$30.92	4.650%	$32.3578	$32.36	$32.35	$32.40
Purchase #4	$191.83	13.384%	$217.5045	$217.50	$217.50	$217.50
Purchase #5	$229.74	6.440%	$244.5353	$244.54	$244.55	$244.50
Purchase #6	$10.82	13.607%	$12.2923	$12.29	$12.30	$12.30
Purchase #7	$142.44	9.758%	$156.3393	$156.34	$156.35	$156.30
7 purchase totals =	$869.51		$957.6386	$957.64	$957.65	$957.60