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	$244.47	9.854%	$268.5601	$268.56	$268.55	$268.60
Purchase #2	$73.47	5.232%	$77.314	$77.31	$77.30	$77.30
Purchase #3	$106.51	12.596%	$119.926	$119.93	$119.95	$119.90
Purchase #4	$139.78	3.459%	$144.615	$144.62	$144.60	$144.60
Purchase #5	$211.85	4.269%	$220.8939	$220.89	$220.90	$220.90
Purchase #6	$95.51	4.472%	$99.7812	$99.78	$99.80	$99.80
Purchase #7	$186.65	6.780%	$199.3049	$199.30	$199.30	$199.30
7 purchase totals =	$1,058.24		$1,130.3951	$1,130.39	$1,130.40	$1,130.40