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	$33.34	11.451%	$37.1578	$37.16	$37.15	$37.20
Purchase #2	$103.62	7.222%	$111.1034	$111.10	$111.10	$111.10
Purchase #3	$194.78	8.293%	$210.9331	$210.93	$210.95	$210.90
Purchase #4	$241.44	8.229%	$261.3081	$261.31	$261.30	$261.30
Purchase #5	$217.81	10.530%	$240.7454	$240.75	$240.75	$240.70
Purchase #6	$94.91	7.710%	$102.2276	$102.23	$102.25	$102.20
Purchase #7	$171.59	11.827%	$191.8839	$191.88	$191.90	$191.90
7 purchase totals =	$1,057.49		$1,155.3593	$1,155.36	$1,155.40	$1,155.30