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	$57.32	11.492%	$63.9072	$63.91	$63.90	$63.90
Purchase #2	$245.49	3.662%	$254.4798	$254.48	$254.50	$254.50
Purchase #3	$243.45	3.115%	$251.0335	$251.03	$251.05	$251.00
Purchase #4	$182.96	6.504%	$194.8597	$194.86	$194.85	$194.90
Purchase #5	$204.53	6.807%	$218.4524	$218.45	$218.45	$218.50
Purchase #6	$38.74	8.798%	$42.1483	$42.15	$42.15	$42.10
Purchase #7	$31.84	12.533%	$35.8305	$35.83	$35.85	$35.80
7 purchase totals =	$1,004.33		$1,060.7114	$1,060.71	$1,060.75	$1,060.70