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	$179.89	8.821%	$195.7581	$195.76	$195.75	$195.80
Purchase #2	$185.43	3.226%	$191.412	$191.41	$191.40	$191.40
Purchase #3	$22.67	9.272%	$24.772	$24.77	$24.75	$24.80
Purchase #4	$147.30	11.715%	$164.5562	$164.56	$164.55	$164.60
Purchase #5	$69.49	12.426%	$78.1248	$78.12	$78.10	$78.10
Purchase #6	$162.43	3.625%	$168.3181	$168.32	$168.30	$168.30
Purchase #7	$86.94	6.142%	$92.2799	$92.28	$92.30	$92.30
7 purchase totals =	$854.15		$915.2211	$915.22	$915.15	$915.30