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	$69.25	10.424%	$76.4686	$76.47	$76.45	$76.50
Purchase #2	$125.53	6.142%	$133.2401	$133.24	$133.25	$133.20
Purchase #3	$53.65	11.246%	$59.6835	$59.68	$59.70	$59.70
Purchase #4	$180.64	5.378%	$190.3548	$190.35	$190.35	$190.40
Purchase #5	$131.92	7.647%	$142.0079	$142.01	$142.00	$142.00
Purchase #6	$209.32	6.554%	$223.0388	$223.04	$223.05	$223.00
Purchase #7	$92.46	7.423%	$99.3233	$99.32	$99.30	$99.30
7 purchase totals =	$862.77		$924.1170	$924.11	$924.10	$924.10