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	$164.75	13.559%	$187.0885	$187.09	$187.10	$187.10
Purchase #2	$39.28	9.425%	$42.9821	$42.98	$43.00	$43.00
Purchase #3	$76.67	5.109%	$80.5871	$80.59	$80.60	$80.60
Purchase #4	$164.43	4.445%	$171.7389	$171.74	$171.75	$171.70
Purchase #5	$145.59	10.363%	$160.6775	$160.68	$160.70	$160.70
Purchase #6	$139.72	5.218%	$147.0106	$147.01	$147.00	$147.00
Purchase #7	$26.72	5.741%	$28.254	$28.25	$28.25	$28.30
7 purchase totals =	$757.16		$818.3387	$818.34	$818.40	$818.40