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	$41.31	4.413%	$43.133	$43.13	$43.15	$43.10
Purchase #2	$195.59	10.409%	$215.949	$215.95	$215.95	$215.90
Purchase #3	$78.43	10.539%	$86.6957	$86.70	$86.70	$86.70
Purchase #4	$77.43	6.571%	$82.5179	$82.52	$82.50	$82.50
Purchase #5	$73.29	6.811%	$78.2818	$78.28	$78.30	$78.30
Purchase #6	$31.75	6.315%	$33.755	$33.76	$33.75	$33.80
Purchase #7	$76.40	10.706%	$84.5794	$84.58	$84.60	$84.60
7 purchase totals =	$574.20		$624.9118	$624.92	$624.95	$624.90