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	$148.57	11.596%	$165.7982	$165.80	$165.80	$165.80
Purchase #2	$245.77	7.546%	$264.3158	$264.32	$264.30	$264.30
Purchase #3	$29.85	13.264%	$33.8093	$33.81	$33.80	$33.80
Purchase #4	$125.71	4.684%	$131.5983	$131.60	$131.60	$131.60
Purchase #5	$60.52	3.755%	$62.7925	$62.79	$62.80	$62.80
Purchase #6	$170.34	9.231%	$186.0641	$186.06	$186.05	$186.10
Purchase #7	$51.50	13.622%	$58.5153	$58.52	$58.50	$58.50
7 purchase totals =	$832.26		$902.8935	$902.90	$902.85	$902.90