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	$98.48	5.487%	$103.8836	$103.88	$103.90	$103.90
Purchase #2	$162.91	12.452%	$183.1956	$183.20	$183.20	$183.20
Purchase #3	$176.41	5.381%	$185.9026	$185.90	$185.90	$185.90
Purchase #4	$178.78	9.833%	$196.3594	$196.36	$196.35	$196.40
Purchase #5	$246.72	8.765%	$268.345	$268.35	$268.35	$268.30
Purchase #6	$138.33	13.297%	$156.7237	$156.72	$156.70	$156.70
Purchase #7	$100.66	3.105%	$103.7855	$103.79	$103.80	$103.80
7 purchase totals =	$1,102.29		$1,198.1954	$1,198.20	$1,198.20	$1,198.20