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	$55.86	13.330%	$63.3061	$63.31	$63.30	$63.30
Purchase #2	$88.94	3.807%	$92.3259	$92.33	$92.35	$92.30
Purchase #3	$101.83	7.288%	$109.2514	$109.25	$109.25	$109.30
Purchase #4	$79.75	3.102%	$82.2238	$82.22	$82.20	$82.20
Purchase #5	$224.26	5.171%	$235.8565	$235.86	$235.85	$235.90
Purchase #6	$51.60	6.158%	$54.7775	$54.78	$54.80	$54.80
Purchase #7	$174.66	7.681%	$188.0756	$188.08	$188.10	$188.10
7 purchase totals =	$776.90		$825.8168	$825.83	$825.85	$825.90