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	$154.43	9.380%	$168.9155	$168.92	$168.90	$168.90
Purchase #2	$66.53	7.461%	$71.4938	$71.49	$71.50	$71.50
Purchase #3	$160.32	3.176%	$165.4118	$165.41	$165.40	$165.40
Purchase #4	$164.81	8.682%	$179.1188	$179.12	$179.10	$179.10
Purchase #5	$56.34	4.780%	$59.0331	$59.03	$59.05	$59.00
Purchase #6	$187.80	3.301%	$193.9993	$194.00	$194.00	$194.00
Purchase #7	$176.66	9.568%	$193.5628	$193.56	$193.55	$193.60
7 purchase totals =	$966.89		$1,031.5351	$1,031.53	$1,031.50	$1,031.50