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	$203.35	6.803%	$217.1839	$217.18	$217.20	$217.20
Purchase #2	$139.39	9.326%	$152.3895	$152.39	$152.40	$152.40
Purchase #3	$29.78	5.415%	$31.3926	$31.39	$31.40	$31.40
Purchase #4	$59.42	8.546%	$64.498	$64.50	$64.50	$64.50
Purchase #5	$210.91	5.409%	$222.3181	$222.32	$222.30	$222.30
Purchase #6	$68.76	4.265%	$71.6926	$71.69	$71.70	$71.70
Purchase #7	$242.67	7.118%	$259.9433	$259.94	$259.95	$259.90
7 purchase totals =	$954.28		$1,019.4180	$1,019.41	$1,019.45	$1,019.40