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	$99.38	6.350%	$105.6906	$105.69	$105.70	$105.70
Purchase #2	$29.26	12.412%	$32.8918	$32.89	$32.90	$32.90
Purchase #3	$122.92	5.229%	$129.3475	$129.35	$129.35	$129.30
Purchase #4	$221.64	13.771%	$252.162	$252.16	$252.15	$252.20
Purchase #5	$152.61	6.332%	$162.2733	$162.27	$162.25	$162.30
Purchase #6	$210.54	7.421%	$226.1642	$226.16	$226.15	$226.20
Purchase #7	$147.55	6.330%	$156.8899	$156.89	$156.90	$156.90
7 purchase totals =	$983.90		$1,065.4193	$1,065.41	$1,065.40	$1,065.50