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	$95.95	9.687%	$105.2447	$105.24	$105.25	$105.20
Purchase #2	$10.90	5.582%	$11.5084	$11.51	$11.50	$11.50
Purchase #3	$115.46	10.654%	$127.7611	$127.76	$127.75	$127.80
Purchase #4	$92.74	11.406%	$103.3179	$103.32	$103.30	$103.30
Purchase #5	$41.99	6.792%	$44.842	$44.84	$44.85	$44.80
Purchase #6	$146.31	12.282%	$164.2798	$164.28	$164.30	$164.30
Purchase #7	$87.70	12.261%	$98.4529	$98.45	$98.45	$98.50
7 purchase totals =	$591.05		$655.4068	$655.40	$655.40	$655.40