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	$56.92	8.844%	$61.954	$61.95	$61.95	$62.00
Purchase #2	$234.50	6.550%	$249.8598	$249.86	$249.85	$249.90
Purchase #3	$215.40	11.722%	$240.6492	$240.65	$240.65	$240.60
Purchase #4	$88.64	11.144%	$98.518	$98.52	$98.50	$98.50
Purchase #5	$137.56	11.610%	$153.5307	$153.53	$153.55	$153.50
Purchase #6	$87.61	13.212%	$99.185	$99.19	$99.20	$99.20
Purchase #7	$12.96	4.871%	$13.5913	$13.59	$13.60	$13.60
7 purchase totals =	$833.59		$917.2880	$917.29	$917.30	$917.30