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	$247.79	8.544%	$268.9612	$268.96	$268.95	$269.00
Purchase #2	$238.96	7.293%	$256.3874	$256.39	$256.40	$256.40
Purchase #3	$8.32	12.743%	$9.3802	$9.38	$9.40	$9.40
Purchase #4	$48.92	12.543%	$55.056	$55.06	$55.05	$55.10
Purchase #5	$172.33	13.860%	$196.2149	$196.21	$196.20	$196.20
Purchase #6	$207.87	3.700%	$215.5612	$215.56	$215.55	$215.60
Purchase #7	$18.63	12.796%	$21.0139	$21.01	$21.00	$21.00
7 purchase totals =	$942.82		$1,022.5748	$1,022.57	$1,022.55	$1,022.70