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	$78.30	9.463%	$85.7095	$85.71	$85.70	$85.70
Purchase #2	$203.83	11.703%	$227.6842	$227.68	$227.70	$227.70
Purchase #3	$180.37	11.334%	$200.8131	$200.81	$200.80	$200.80
Purchase #4	$70.88	11.312%	$78.8979	$78.90	$78.90	$78.90
Purchase #5	$37.60	11.318%	$41.8556	$41.86	$41.85	$41.90
Purchase #6	$245.95	7.459%	$264.2954	$264.30	$264.30	$264.30
Purchase #7	$188.30	6.385%	$200.323	$200.32	$200.30	$200.30
7 purchase totals =	$1,005.23		$1,099.5787	$1,099.58	$1,099.55	$1,099.60