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	$152.91	6.373%	$162.655	$162.66	$162.65	$162.70
Purchase #2	$18.64	3.576%	$19.3066	$19.31	$19.30	$19.30
Purchase #3	$173.83	10.387%	$191.8857	$191.89	$191.90	$191.90
Purchase #4	$85.28	13.288%	$96.612	$96.61	$96.60	$96.60
Purchase #5	$248.92	9.748%	$273.1847	$273.18	$273.20	$273.20
Purchase #6	$200.96	5.411%	$211.8339	$211.83	$211.85	$211.80
Purchase #7	$37.36	8.852%	$40.6671	$40.67	$40.65	$40.70
7 purchase totals =	$917.90		$996.1450	$996.15	$996.15	$996.20