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	$23.59	9.108%	$25.7386	$25.74	$25.75	$25.70
Purchase #2	$72.73	12.866%	$82.0874	$82.09	$82.10	$82.10
Purchase #3	$193.43	9.165%	$211.1579	$211.16	$211.15	$211.20
Purchase #4	$120.45	6.229%	$127.9528	$127.95	$127.95	$128.00
Purchase #5	$86.62	5.397%	$91.2949	$91.29	$91.30	$91.30
Purchase #6	$61.53	5.410%	$64.8588	$64.86	$64.85	$64.90
Purchase #7	$116.55	12.357%	$130.9521	$130.95	$130.95	$131.00
7 purchase totals =	$674.90		$734.0425	$734.04	$734.05	$734.20