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	$53.61	5.713%	$56.6727	$56.67	$56.65	$56.70
Purchase #2	$21.60	11.404%	$24.0633	$24.06	$24.05	$24.10
Purchase #3	$43.72	7.572%	$47.0305	$47.03	$47.05	$47.00
Purchase #4	$221.88	9.655%	$243.3025	$243.30	$243.30	$243.30
Purchase #5	$39.87	5.211%	$41.9476	$41.95	$41.95	$41.90
Purchase #6	$57.64	3.521%	$59.6695	$59.67	$59.65	$59.70
Purchase #7	$132.60	7.515%	$142.5649	$142.56	$142.55	$142.60
7 purchase totals =	$570.92		$615.2510	$615.24	$615.20	$615.30