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	$110.47	6.519%	$117.6715	$117.67	$117.65	$117.70
Purchase #2	$54.67	6.330%	$58.1306	$58.13	$58.15	$58.10
Purchase #3	$186.71	5.193%	$196.4059	$196.41	$196.40	$196.40
Purchase #4	$78.37	13.872%	$89.2415	$89.24	$89.25	$89.20
Purchase #5	$228.91	4.328%	$238.8172	$238.82	$238.80	$238.80
Purchase #6	$214.63	5.708%	$226.8811	$226.88	$226.90	$226.90
Purchase #7	$18.82	13.205%	$21.3052	$21.31	$21.30	$21.30
7 purchase totals =	$892.58		$948.4530	$948.46	$948.45	$948.40