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	$78.78	10.250%	$86.855	$86.86	$86.85	$86.90
Purchase #2	$98.82	5.305%	$104.0624	$104.06	$104.05	$104.10
Purchase #3	$69.82	11.263%	$77.6838	$77.68	$77.70	$77.70
Purchase #4	$196.76	4.345%	$205.3092	$205.31	$205.30	$205.30
Purchase #5	$51.44	7.677%	$55.389	$55.39	$55.40	$55.40
Purchase #6	$42.51	7.159%	$45.5533	$45.55	$45.55	$45.60
Purchase #7	$133.48	5.778%	$141.1925	$141.19	$141.20	$141.20
7 purchase totals =	$671.61		$716.0452	$716.04	$716.05	$716.20