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	$142.56	6.342%	$151.6012	$151.60	$151.60	$151.60
Purchase #2	$70.45	8.687%	$76.57	$76.57	$76.55	$76.60
Purchase #3	$188.82	8.257%	$204.4109	$204.41	$204.40	$204.40
Purchase #4	$88.89	3.468%	$91.9727	$91.97	$91.95	$92.00
Purchase #5	$56.61	4.702%	$59.2718	$59.27	$59.25	$59.30
Purchase #6	$129.66	12.340%	$145.66	$145.66	$145.65	$145.70
Purchase #7	$46.96	8.601%	$50.999	$51.00	$51.00	$51.00
7 purchase totals =	$723.95		$780.4856	$780.48	$780.40	$780.60