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	$111.89	5.803%	$118.383	$118.38	$118.40	$118.40
Purchase #2	$94.72	4.676%	$99.1491	$99.15	$99.15	$99.10
Purchase #3	$45.62	12.659%	$51.395	$51.40	$51.40	$51.40
Purchase #4	$19.54	12.661%	$22.014	$22.01	$22.00	$22.00
Purchase #5	$179.66	6.682%	$191.6649	$191.66	$191.65	$191.70
Purchase #6	$236.35	12.489%	$265.8678	$265.87	$265.85	$265.90
Purchase #7	$72.65	12.592%	$81.7981	$81.80	$81.80	$81.80
7 purchase totals =	$760.43		$830.2719	$830.27	$830.25	$830.30