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	$172.82	13.570%	$196.2717	$196.27	$196.25	$196.30
Purchase #2	$152.33	10.810%	$168.7969	$168.80	$168.80	$168.80
Purchase #3	$17.75	8.392%	$19.2396	$19.24	$19.25	$19.20
Purchase #4	$77.51	6.354%	$82.435	$82.44	$82.45	$82.40
Purchase #5	$250.39	13.767%	$284.8612	$284.86	$284.85	$284.90
Purchase #6	$211.52	5.699%	$223.5745	$223.57	$223.55	$223.60
Purchase #7	$68.98	8.676%	$74.9647	$74.96	$74.95	$75.00
7 purchase totals =	$951.30		$1,050.1436	$1,050.14	$1,050.10	$1,050.20