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	$111.90	4.496%	$116.931	$116.93	$116.95	$116.90
Purchase #2	$91.27	11.184%	$101.4776	$101.48	$101.50	$101.50
Purchase #3	$119.53	4.500%	$124.9089	$124.91	$124.90	$124.90
Purchase #4	$167.90	4.276%	$175.0794	$175.08	$175.10	$175.10
Purchase #5	$164.31	9.505%	$179.9277	$179.93	$179.95	$179.90
Purchase #6	$61.32	9.800%	$67.3294	$67.33	$67.35	$67.30
Purchase #7	$148.55	4.588%	$155.3655	$155.37	$155.35	$155.40
7 purchase totals =	$864.78		$921.0195	$921.03	$921.10	$921.00