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	$93.81	10.536%	$103.6938	$103.69	$103.70	$103.70
Purchase #2	$225.63	8.635%	$245.1132	$245.11	$245.10	$245.10
Purchase #3	$127.60	3.156%	$131.6271	$131.63	$131.65	$131.60
Purchase #4	$103.66	8.361%	$112.327	$112.33	$112.35	$112.30
Purchase #5	$86.76	8.425%	$94.0695	$94.07	$94.05	$94.10
Purchase #6	$30.78	4.200%	$32.0728	$32.07	$32.05	$32.10
Purchase #7	$92.70	7.820%	$99.9491	$99.95	$99.95	$99.90
7 purchase totals =	$760.94		$818.8525	$818.85	$818.85	$818.80