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	$204.97	6.365%	$218.0163	$218.02	$218.00	$218.00
Purchase #2	$59.73	3.289%	$61.6945	$61.69	$61.70	$61.70
Purchase #3	$214.94	3.750%	$223.0003	$223.00	$223.00	$223.00
Purchase #4	$91.95	12.350%	$103.3058	$103.31	$103.30	$103.30
Purchase #5	$243.59	11.320%	$271.1644	$271.16	$271.15	$271.20
Purchase #6	$14.27	8.284%	$15.4521	$15.45	$15.45	$15.50
Purchase #7	$171.46	8.639%	$186.2724	$186.27	$186.25	$186.30
7 purchase totals =	$1,000.91		$1,078.9058	$1,078.90	$1,078.85	$1,079.00