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	$68.98	4.287%	$71.9372	$71.94	$71.95	$71.90
Purchase #2	$226.28	7.187%	$242.5427	$242.54	$242.55	$242.50
Purchase #3	$198.73	5.859%	$210.3736	$210.37	$210.35	$210.40
Purchase #4	$106.95	4.180%	$111.4205	$111.42	$111.40	$111.40
Purchase #5	$49.63	7.246%	$53.2262	$53.23	$53.25	$53.20
Purchase #6	$97.67	4.336%	$101.905	$101.91	$101.90	$101.90
Purchase #7	$232.42	8.374%	$251.8829	$251.88	$251.90	$251.90
7 purchase totals =	$980.66		$1,043.2881	$1,043.29	$1,043.30	$1,043.20