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	$38.58	7.339%	$41.4114	$41.41	$41.40	$41.40
Purchase #2	$75.40	9.490%	$82.5555	$82.56	$82.55	$82.60
Purchase #3	$178.25	10.468%	$196.9092	$196.91	$196.90	$196.90
Purchase #4	$148.95	10.312%	$164.3097	$164.31	$164.30	$164.30
Purchase #5	$24.67	12.852%	$27.8406	$27.84	$27.85	$27.80
Purchase #6	$113.64	11.263%	$126.4393	$126.44	$126.45	$126.40
Purchase #7	$57.92	5.841%	$61.3031	$61.30	$61.30	$61.30
7 purchase totals =	$637.41		$700.7688	$700.77	$700.75	$700.70