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	$205.57	13.467%	$233.2541	$233.25	$233.25	$233.30
Purchase #2	$59.62	4.237%	$62.1461	$62.15	$62.15	$62.10
Purchase #3	$233.48	4.219%	$243.3305	$243.33	$243.35	$243.30
Purchase #4	$235.89	8.417%	$255.7449	$255.74	$255.75	$255.70
Purchase #5	$170.49	6.214%	$181.0842	$181.08	$181.10	$181.10
Purchase #6	$156.59	7.362%	$168.1182	$168.12	$168.10	$168.10
Purchase #7	$109.77	8.496%	$119.0961	$119.10	$119.10	$119.10
7 purchase totals =	$1,171.41		$1,262.7741	$1,262.77	$1,262.80	$1,262.70