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	$202.59	6.682%	$216.1271	$216.13	$216.15	$216.10
Purchase #2	$233.73	11.845%	$261.4153	$261.42	$261.40	$261.40
Purchase #3	$55.39	12.660%	$62.4024	$62.40	$62.40	$62.40
Purchase #4	$19.32	10.623%	$21.3724	$21.37	$21.35	$21.40
Purchase #5	$20.81	6.658%	$22.1955	$22.20	$22.20	$22.20
Purchase #6	$203.28	12.711%	$229.1189	$229.12	$229.10	$229.10
Purchase #7	$184.80	6.498%	$196.8083	$196.81	$196.80	$196.80
7 purchase totals =	$919.92		$1,009.4399	$1,009.45	$1,009.40	$1,009.40