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	$76.67	12.236%	$86.0513	$86.05	$86.05	$86.10
Purchase #2	$209.32	4.497%	$218.7331	$218.73	$218.75	$218.70
Purchase #3	$76.89	13.679%	$87.4078	$87.41	$87.40	$87.40
Purchase #4	$115.41	6.818%	$123.2787	$123.28	$123.30	$123.30
Purchase #5	$88.83	12.110%	$99.5873	$99.59	$99.60	$99.60
Purchase #6	$234.72	11.867%	$262.5742	$262.57	$262.55	$262.60
Purchase #7	$174.59	11.843%	$195.2667	$195.27	$195.25	$195.30
7 purchase totals =	$976.43		$1,072.8991	$1,072.90	$1,072.90	$1,073.00