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	$156.58	4.260%	$163.2503	$163.25	$163.25	$163.30
Purchase #2	$230.41	3.444%	$238.3453	$238.35	$238.35	$238.30
Purchase #3	$44.89	13.506%	$50.9528	$50.95	$50.95	$51.00
Purchase #4	$165.28	5.347%	$174.1175	$174.12	$174.10	$174.10
Purchase #5	$96.79	7.379%	$103.9321	$103.93	$103.95	$103.90
Purchase #6	$82.45	11.331%	$91.7924	$91.79	$91.80	$91.80
Purchase #7	$189.80	3.614%	$196.6594	$196.66	$196.65	$196.70
7 purchase totals =	$966.20		$1,019.0498	$1,019.05	$1,019.05	$1,019.10