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	$98.92	7.544%	$106.3825	$106.38	$106.40	$106.40
Purchase #2	$211.37	5.495%	$222.9848	$222.98	$223.00	$223.00
Purchase #3	$39.31	3.762%	$40.7888	$40.79	$40.80	$40.80
Purchase #4	$115.96	10.176%	$127.7601	$127.76	$127.75	$127.80
Purchase #5	$33.45	12.524%	$37.6393	$37.64	$37.65	$37.60
Purchase #6	$232.90	9.853%	$255.8476	$255.85	$255.85	$255.80
Purchase #7	$66.44	5.188%	$69.8869	$69.89	$69.90	$69.90
7 purchase totals =	$798.35		$861.2900	$861.29	$861.35	$861.30