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	$129.32	9.581%	$141.7101	$141.71	$141.70	$141.70
Purchase #2	$96.96	3.275%	$100.1354	$100.14	$100.15	$100.10
Purchase #3	$113.43	12.829%	$127.9819	$127.98	$128.00	$128.00
Purchase #4	$227.79	13.596%	$258.7603	$258.76	$258.75	$258.80
Purchase #5	$80.72	6.131%	$85.6689	$85.67	$85.65	$85.70
Purchase #6	$158.87	3.436%	$164.3288	$164.33	$164.35	$164.30
Purchase #7	$207.60	9.323%	$226.9545	$226.95	$226.95	$227.00
7 purchase totals =	$1,014.69		$1,105.5399	$1,105.54	$1,105.55	$1,105.60