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	$221.98	7.123%	$237.7916	$237.79	$237.80	$237.80
Purchase #2	$106.63	8.267%	$115.4451	$115.45	$115.45	$115.40
Purchase #3	$129.48	9.846%	$142.2286	$142.23	$142.25	$142.20
Purchase #4	$102.70	8.172%	$111.0926	$111.09	$111.10	$111.10
Purchase #5	$41.66	12.126%	$46.7117	$46.71	$46.70	$46.70
Purchase #6	$155.51	10.529%	$171.8836	$171.88	$171.90	$171.90
Purchase #7	$168.72	5.552%	$178.0873	$178.09	$178.10	$178.10
7 purchase totals =	$926.68		$1,003.2405	$1,003.24	$1,003.30	$1,003.20