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	$222.73	7.788%	$240.0762	$240.08	$240.10	$240.10
Purchase #2	$234.69	4.163%	$244.4601	$244.46	$244.45	$244.50
Purchase #3	$168.37	12.799%	$189.9197	$189.92	$189.90	$189.90
Purchase #4	$37.69	9.693%	$41.3433	$41.34	$41.35	$41.30
Purchase #5	$36.40	9.847%	$39.9843	$39.98	$40.00	$40.00
Purchase #6	$113.27	12.381%	$127.294	$127.29	$127.30	$127.30
Purchase #7	$227.94	7.808%	$245.7376	$245.74	$245.75	$245.70
7 purchase totals =	$1,041.09		$1,128.8152	$1,128.81	$1,128.85	$1,128.80