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	$144.93	4.813%	$151.9055	$151.91	$151.90	$151.90
Purchase #2	$182.67	9.681%	$200.3543	$200.35	$200.35	$200.40
Purchase #3	$199.29	10.256%	$219.7292	$219.73	$219.75	$219.70
Purchase #4	$118.63	10.473%	$131.0541	$131.05	$131.05	$131.10
Purchase #5	$81.70	12.306%	$91.754	$91.75	$91.75	$91.80
Purchase #6	$119.33	10.553%	$131.9229	$131.92	$131.90	$131.90
Purchase #7	$176.84	5.219%	$186.0693	$186.07	$186.05	$186.10
7 purchase totals =	$1,023.39		$1,112.7893	$1,112.78	$1,112.75	$1,112.90