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	$114.88	11.681%	$128.2991	$128.30	$128.30	$128.30
Purchase #2	$120.41	6.547%	$128.2932	$128.29	$128.30	$128.30
Purchase #3	$99.68	4.667%	$104.3321	$104.33	$104.35	$104.30
Purchase #4	$242.97	12.453%	$273.2271	$273.23	$273.25	$273.20
Purchase #5	$156.95	9.164%	$171.3329	$171.33	$171.35	$171.30
Purchase #6	$96.81	8.156%	$104.7058	$104.71	$104.70	$104.70
Purchase #7	$94.44	6.745%	$100.81	$100.81	$100.80	$100.80
7 purchase totals =	$926.14		$1,011.0002	$1,011.00	$1,011.05	$1,010.90