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	$198.74	5.575%	$209.8198	$209.82	$209.80	$209.80
Purchase #2	$129.73	11.644%	$144.8358	$144.84	$144.85	$144.80
Purchase #3	$156.77	12.588%	$176.5042	$176.50	$176.50	$176.50
Purchase #4	$72.46	5.498%	$76.4439	$76.44	$76.45	$76.40
Purchase #5	$126.56	12.303%	$142.1307	$142.13	$142.15	$142.10
Purchase #6	$233.59	3.549%	$241.8801	$241.88	$241.90	$241.90
Purchase #7	$48.97	6.613%	$52.2084	$52.21	$52.20	$52.20
7 purchase totals =	$966.82		$1,043.8229	$1,043.82	$1,043.85	$1,043.70