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	$164.26	11.610%	$183.3306	$183.33	$183.35	$183.30
Purchase #2	$88.89	12.627%	$100.1141	$100.11	$100.10	$100.10
Purchase #3	$98.90	10.714%	$109.4961	$109.50	$109.50	$109.50
Purchase #4	$213.89	3.819%	$222.0585	$222.06	$222.05	$222.10
Purchase #5	$148.62	4.281%	$154.9824	$154.98	$155.00	$155.00
Purchase #6	$187.66	10.434%	$207.2404	$207.24	$207.25	$207.20
Purchase #7	$47.31	12.520%	$53.2332	$53.23	$53.25	$53.20
7 purchase totals =	$949.53		$1,030.4553	$1,030.45	$1,030.50	$1,030.40