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	$177.76	7.273%	$190.6885	$190.69	$190.70	$190.70
Purchase #2	$248.74	11.150%	$276.4745	$276.47	$276.45	$276.50
Purchase #3	$173.47	13.223%	$196.4079	$196.41	$196.40	$196.40
Purchase #4	$33.93	9.224%	$37.0597	$37.06	$37.05	$37.10
Purchase #5	$98.74	9.850%	$108.4659	$108.47	$108.45	$108.50
Purchase #6	$78.96	10.113%	$86.9452	$86.95	$86.95	$86.90
Purchase #7	$231.68	11.793%	$259.002	$259.00	$259.00	$259.00
7 purchase totals =	$1,043.28		$1,155.0437	$1,155.05	$1,155.00	$1,155.10