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	$64.93	5.365%	$68.4135	$68.41	$68.40	$68.40
Purchase #2	$224.39	8.454%	$243.3599	$243.36	$243.35	$243.40
Purchase #3	$200.88	5.690%	$212.3101	$212.31	$212.30	$212.30
Purchase #4	$39.88	10.239%	$43.9633	$43.96	$43.95	$44.00
Purchase #5	$248.85	10.452%	$274.8598	$274.86	$274.85	$274.90
Purchase #6	$55.31	7.200%	$59.2923	$59.29	$59.30	$59.30
Purchase #7	$183.41	8.166%	$198.3873	$198.39	$198.40	$198.40
7 purchase totals =	$1,017.65		$1,100.5862	$1,100.58	$1,100.55	$1,100.70