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	$125.25	6.231%	$133.0543	$133.05	$133.05	$133.10
Purchase #2	$31.91	12.360%	$35.8541	$35.85	$35.85	$35.90
Purchase #3	$176.64	8.302%	$191.3047	$191.30	$191.30	$191.30
Purchase #4	$217.93	7.373%	$233.998	$234.00	$234.00	$234.00
Purchase #5	$223.25	6.802%	$238.4355	$238.44	$238.45	$238.40
Purchase #6	$70.33	9.336%	$76.896	$76.90	$76.90	$76.90
Purchase #7	$140.54	8.351%	$152.2765	$152.28	$152.30	$152.30
7 purchase totals =	$985.85		$1,061.8191	$1,061.82	$1,061.85	$1,061.90