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	$147.50	7.225%	$158.1569	$158.16	$158.15	$158.20
Purchase #2	$139.26	12.113%	$156.1286	$156.13	$156.15	$156.10
Purchase #3	$15.31	11.405%	$17.0561	$17.06	$17.05	$17.10
Purchase #4	$246.81	10.632%	$273.0508	$273.05	$273.05	$273.10
Purchase #5	$162.86	4.492%	$170.1757	$170.18	$170.20	$170.20
Purchase #6	$173.76	10.369%	$191.7772	$191.78	$191.80	$191.80
Purchase #7	$41.41	3.334%	$42.7906	$42.79	$42.80	$42.80
7 purchase totals =	$926.91		$1,009.1359	$1,009.15	$1,009.20	$1,009.30