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	$172.62	9.437%	$188.9101	$188.91	$188.90	$188.90
Purchase #2	$199.48	5.429%	$210.3098	$210.31	$210.30	$210.30
Purchase #3	$94.86	10.654%	$104.9664	$104.97	$104.95	$105.00
Purchase #4	$140.37	9.757%	$154.0659	$154.07	$154.05	$154.10
Purchase #5	$218.93	4.190%	$228.1032	$228.10	$228.10	$228.10
Purchase #6	$6.57	11.592%	$7.3316	$7.33	$7.35	$7.30
Purchase #7	$160.68	4.312%	$167.6085	$167.61	$167.60	$167.60
7 purchase totals =	$993.51		$1,061.2955	$1,061.30	$1,061.25	$1,061.30