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	$206.80	5.490%	$218.1533	$218.15	$218.15	$218.20
Purchase #2	$134.79	3.728%	$139.815	$139.82	$139.80	$139.80
Purchase #3	$117.98	11.119%	$131.0982	$131.10	$131.10	$131.10
Purchase #4	$62.70	13.134%	$70.935	$70.94	$70.95	$70.90
Purchase #5	$229.38	4.872%	$240.5554	$240.56	$240.55	$240.60
Purchase #6	$222.76	10.381%	$245.8847	$245.88	$245.90	$245.90
Purchase #7	$53.63	9.390%	$58.6659	$58.67	$58.65	$58.70
7 purchase totals =	$1,028.04		$1,105.1075	$1,105.12	$1,105.10	$1,105.20