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	$151.66	13.536%	$172.1887	$172.19	$172.20	$172.20
Purchase #2	$93.91	5.219%	$98.8112	$98.81	$98.80	$98.80
Purchase #3	$148.61	5.368%	$156.5874	$156.59	$156.60	$156.60
Purchase #4	$209.89	6.308%	$223.1299	$223.13	$223.15	$223.10
Purchase #5	$56.47	10.293%	$62.2825	$62.28	$62.30	$62.30
Purchase #6	$142.96	11.867%	$159.9251	$159.93	$159.95	$159.90
Purchase #7	$82.26	3.416%	$85.07	$85.07	$85.05	$85.10
7 purchase totals =	$885.76		$957.9948	$958.00	$958.05	$958.00