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	$135.44	7.584%	$145.7118	$145.71	$145.70	$145.70
Purchase #2	$88.37	7.641%	$95.1224	$95.12	$95.10	$95.10
Purchase #3	$179.46	9.649%	$196.7761	$196.78	$196.80	$196.80
Purchase #4	$71.58	11.568%	$79.8604	$79.86	$79.85	$79.90
Purchase #5	$205.94	9.307%	$225.1068	$225.11	$225.10	$225.10
Purchase #6	$158.90	13.129%	$179.762	$179.76	$179.75	$179.80
Purchase #7	$213.31	13.379%	$241.8487	$241.85	$241.85	$241.80
7 purchase totals =	$1,053.00		$1,164.1882	$1,164.19	$1,164.15	$1,164.20