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	$72.28	8.734%	$78.5929	$78.59	$78.60	$78.60
Purchase #2	$9.89	5.641%	$10.4479	$10.45	$10.45	$10.40
Purchase #3	$245.74	10.767%	$272.1988	$272.20	$272.20	$272.20
Purchase #4	$231.35	9.735%	$253.8719	$253.87	$253.85	$253.90
Purchase #5	$51.76	11.824%	$57.8801	$57.88	$57.90	$57.90
Purchase #6	$139.40	7.532%	$149.8996	$149.90	$149.90	$149.90
Purchase #7	$167.44	8.151%	$181.088	$181.09	$181.10	$181.10
7 purchase totals =	$917.86		$1,003.9792	$1,003.98	$1,004.00	$1,004.00