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	$246.46	9.109%	$268.91	$268.91	$268.90	$268.90
Purchase #2	$71.94	6.153%	$76.3665	$76.37	$76.35	$76.40
Purchase #3	$249.83	8.382%	$270.7708	$270.77	$270.75	$270.80
Purchase #4	$173.27	13.329%	$196.3652	$196.37	$196.35	$196.40
Purchase #5	$45.51	6.195%	$48.3293	$48.33	$48.35	$48.30
Purchase #6	$220.28	8.206%	$238.3562	$238.36	$238.35	$238.40
Purchase #7	$51.30	5.648%	$54.1974	$54.20	$54.20	$54.20
7 purchase totals =	$1,058.59		$1,153.2954	$1,153.31	$1,153.25	$1,153.40