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	$83.62	10.143%	$92.1016	$92.10	$92.10	$92.10
Purchase #2	$18.83	10.239%	$20.758	$20.76	$20.75	$20.80
Purchase #3	$41.69	6.582%	$44.434	$44.43	$44.45	$44.40
Purchase #4	$219.70	12.352%	$246.8373	$246.84	$246.85	$246.80
Purchase #5	$51.70	6.178%	$54.894	$54.89	$54.90	$54.90
Purchase #6	$75.58	4.228%	$78.7755	$78.78	$78.80	$78.80
Purchase #7	$241.33	10.735%	$267.2368	$267.24	$267.25	$267.20
7 purchase totals =	$732.45		$805.0372	$805.04	$805.10	$805.00