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	$108.38	3.556%	$112.234	$112.23	$112.25	$112.20
Purchase #2	$234.89	5.493%	$247.7925	$247.79	$247.80	$247.80
Purchase #3	$32.85	6.408%	$34.955	$34.96	$34.95	$35.00
Purchase #4	$33.31	8.375%	$36.0997	$36.10	$36.10	$36.10
Purchase #5	$91.83	13.674%	$104.3868	$104.39	$104.40	$104.40
Purchase #6	$85.52	5.535%	$90.2535	$90.25	$90.25	$90.30
Purchase #7	$141.49	7.506%	$152.1102	$152.11	$152.10	$152.10
7 purchase totals =	$728.27		$777.8317	$777.83	$777.85	$777.90