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	$154.49	7.415%	$165.9454	$165.95	$165.95	$165.90
Purchase #2	$231.75	13.694%	$263.4858	$263.49	$263.50	$263.50
Purchase #3	$123.90	11.582%	$138.2501	$138.25	$138.25	$138.30
Purchase #4	$84.88	6.658%	$90.5313	$90.53	$90.55	$90.50
Purchase #5	$243.44	6.769%	$259.9185	$259.92	$259.90	$259.90
Purchase #6	$141.88	10.320%	$156.522	$156.52	$156.50	$156.50
Purchase #7	$71.58	8.788%	$77.8705	$77.87	$77.85	$77.90
7 purchase totals =	$1,051.92		$1,152.5236	$1,152.53	$1,152.50	$1,152.50