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	$250.93	4.815%	$263.0123	$263.01	$263.00	$263.00
Purchase #2	$40.91	5.147%	$43.0156	$43.02	$43.00	$43.00
Purchase #3	$12.84	13.636%	$14.5909	$14.59	$14.60	$14.60
Purchase #4	$191.73	12.590%	$215.8688	$215.87	$215.85	$215.90
Purchase #5	$91.36	10.327%	$100.7947	$100.79	$100.80	$100.80
Purchase #6	$141.80	6.121%	$150.4796	$150.48	$150.50	$150.50
Purchase #7	$92.26	9.423%	$100.9537	$100.95	$100.95	$101.00
7 purchase totals =	$821.83		$888.7156	$888.71	$888.70	$888.80