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	$83.48	6.666%	$89.0448	$89.04	$89.05	$89.00
Purchase #2	$49.76	7.369%	$53.4268	$53.43	$53.45	$53.40
Purchase #3	$169.73	6.267%	$180.367	$180.37	$180.35	$180.40
Purchase #4	$28.41	8.779%	$30.9041	$30.90	$30.90	$30.90
Purchase #5	$183.32	11.383%	$204.1873	$204.19	$204.20	$204.20
Purchase #6	$136.93	6.718%	$146.129	$146.13	$146.15	$146.10
Purchase #7	$19.47	10.346%	$21.4844	$21.48	$21.50	$21.50
7 purchase totals =	$671.10		$725.5434	$725.54	$725.60	$725.50