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	$88.57	13.404%	$100.4419	$100.44	$100.45	$100.40
Purchase #2	$82.61	8.172%	$89.3609	$89.36	$89.35	$89.40
Purchase #3	$148.35	6.143%	$157.4631	$157.46	$157.45	$157.50
Purchase #4	$216.71	13.214%	$245.3461	$245.35	$245.35	$245.30
Purchase #5	$183.54	12.377%	$206.2567	$206.26	$206.25	$206.30
Purchase #6	$142.36	12.416%	$160.0354	$160.04	$160.05	$160.00
Purchase #7	$99.72	3.611%	$103.3209	$103.32	$103.30	$103.30
7 purchase totals =	$961.86		$1,062.2250	$1,062.23	$1,062.20	$1,062.20