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	$88.89	3.345%	$91.8634	$91.86	$91.85	$91.90
Purchase #2	$210.27	12.524%	$236.6042	$236.60	$236.60	$236.60
Purchase #3	$64.92	8.452%	$70.407	$70.41	$70.40	$70.40
Purchase #4	$32.78	7.719%	$35.3103	$35.31	$35.30	$35.30
Purchase #5	$173.52	7.791%	$187.0389	$187.04	$187.05	$187.00
Purchase #6	$183.27	4.844%	$192.1476	$192.15	$192.15	$192.10
Purchase #7	$187.25	9.152%	$204.3871	$204.39	$204.40	$204.40
7 purchase totals =	$940.90		$1,017.7585	$1,017.76	$1,017.75	$1,017.70