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	$57.60	6.678%	$61.4465	$61.45	$61.45	$61.40
Purchase #2	$103.38	5.507%	$109.0731	$109.07	$109.05	$109.10
Purchase #3	$224.67	4.250%	$234.2185	$234.22	$234.20	$234.20
Purchase #4	$89.53	4.373%	$93.4451	$93.45	$93.45	$93.40
Purchase #5	$30.40	4.774%	$31.8513	$31.85	$31.85	$31.90
Purchase #6	$192.45	6.686%	$205.3172	$205.32	$205.30	$205.30
Purchase #7	$170.69	8.705%	$185.5486	$185.55	$185.55	$185.50
7 purchase totals =	$868.72		$920.9003	$920.91	$920.85	$920.80