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	$141.35	13.373%	$160.2527	$160.25	$160.25	$160.30
Purchase #2	$177.91	7.539%	$191.3226	$191.32	$191.30	$191.30
Purchase #3	$220.67	4.795%	$231.2511	$231.25	$231.25	$231.30
Purchase #4	$39.99	13.265%	$45.2947	$45.29	$45.30	$45.30
Purchase #5	$133.78	10.518%	$147.851	$147.85	$147.85	$147.90
Purchase #6	$137.54	5.745%	$145.4417	$145.44	$145.45	$145.40
Purchase #7	$165.96	11.744%	$185.4503	$185.45	$185.45	$185.50
7 purchase totals =	$1,017.20		$1,106.8641	$1,106.85	$1,106.85	$1,107.00