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	$207.76	11.462%	$231.5735	$231.57	$231.55	$231.60
Purchase #2	$189.42	4.213%	$197.4003	$197.40	$197.40	$197.40
Purchase #3	$91.75	8.340%	$99.402	$99.40	$99.40	$99.40
Purchase #4	$42.62	9.112%	$46.5035	$46.50	$46.50	$46.50
Purchase #5	$59.73	11.655%	$66.6915	$66.69	$66.70	$66.70
Purchase #6	$77.85	9.860%	$85.526	$85.53	$85.55	$85.50
Purchase #7	$37.33	5.310%	$39.3122	$39.31	$39.30	$39.30
7 purchase totals =	$706.46		$766.4090	$766.40	$766.40	$766.40