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	$10.69	4.752%	$11.198	$11.20	$11.20	$11.20
Purchase #2	$56.71	5.490%	$59.8234	$59.82	$59.80	$59.80
Purchase #3	$237.35	12.344%	$266.6485	$266.65	$266.65	$266.60
Purchase #4	$80.25	4.438%	$83.8115	$83.81	$83.80	$83.80
Purchase #5	$41.51	5.735%	$43.8906	$43.89	$43.90	$43.90
Purchase #6	$102.65	7.425%	$110.2718	$110.27	$110.25	$110.30
Purchase #7	$66.84	8.130%	$72.2741	$72.27	$72.25	$72.30
7 purchase totals =	$596.00		$647.9179	$647.91	$647.85	$647.90