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	$119.38	3.750%	$123.8568	$123.86	$123.85	$123.90
Purchase #2	$130.91	10.676%	$144.886	$144.89	$144.90	$144.90
Purchase #3	$201.92	5.396%	$212.8156	$212.82	$212.80	$212.80
Purchase #4	$32.28	11.262%	$35.9154	$35.92	$35.90	$35.90
Purchase #5	$5.88	6.370%	$6.2546	$6.25	$6.25	$6.30
Purchase #6	$61.76	8.666%	$67.1121	$67.11	$67.10	$67.10
Purchase #7	$180.79	5.142%	$190.0862	$190.09	$190.10	$190.10
7 purchase totals =	$732.92		$780.9267	$780.94	$780.90	$781.00