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	$162.30	9.281%	$177.3631	$177.36	$177.35	$177.40
Purchase #2	$235.25	8.757%	$255.8508	$255.85	$255.85	$255.90
Purchase #3	$59.89	13.370%	$67.8973	$67.90	$67.90	$67.90
Purchase #4	$75.65	13.234%	$85.6615	$85.66	$85.65	$85.70
Purchase #5	$117.84	8.757%	$128.1592	$128.16	$128.15	$128.20
Purchase #6	$114.56	12.514%	$128.896	$128.90	$128.90	$128.90
Purchase #7	$141.69	9.629%	$155.3333	$155.33	$155.35	$155.30
7 purchase totals =	$907.18		$999.1612	$999.16	$999.15	$999.30