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	$145.25	13.822%	$165.3265	$165.33	$165.35	$165.30
Purchase #2	$86.35	13.639%	$98.1273	$98.13	$98.15	$98.10
Purchase #3	$191.45	10.167%	$210.9147	$210.91	$210.90	$210.90
Purchase #4	$210.62	4.481%	$220.0579	$220.06	$220.05	$220.10
Purchase #5	$50.48	5.738%	$53.3765	$53.38	$53.40	$53.40
Purchase #6	$250.54	6.102%	$265.828	$265.83	$265.85	$265.80
Purchase #7	$38.47	13.379%	$43.6169	$43.62	$43.60	$43.60
7 purchase totals =	$973.16		$1,057.2478	$1,057.26	$1,057.30	$1,057.20