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	$174.63	12.544%	$196.5356	$196.54	$196.55	$196.50
Purchase #2	$222.62	7.272%	$238.8089	$238.81	$238.80	$238.80
Purchase #3	$242.82	7.828%	$261.8279	$261.83	$261.85	$261.80
Purchase #4	$62.64	13.315%	$70.9805	$70.98	$71.00	$71.00
Purchase #5	$81.73	6.125%	$86.736	$86.74	$86.75	$86.70
Purchase #6	$11.31	9.552%	$12.3903	$12.39	$12.40	$12.40
Purchase #7	$75.43	4.696%	$78.9722	$78.97	$78.95	$79.00
7 purchase totals =	$871.18		$946.2514	$946.26	$946.30	$946.20