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	$197.73	10.689%	$218.8654	$218.87	$218.85	$218.90
Purchase #2	$160.27	9.462%	$175.4347	$175.43	$175.45	$175.40
Purchase #3	$56.64	9.861%	$62.2253	$62.23	$62.25	$62.20
Purchase #4	$227.33	5.787%	$240.4856	$240.49	$240.50	$240.50
Purchase #5	$60.29	6.282%	$64.0774	$64.08	$64.10	$64.10
Purchase #6	$20.44	4.390%	$21.3373	$21.34	$21.35	$21.30
Purchase #7	$69.89	4.168%	$72.803	$72.80	$72.80	$72.80
7 purchase totals =	$792.59		$855.2287	$855.24	$855.30	$855.20