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	$177.72	3.710%	$184.3134	$184.31	$184.30	$184.30
Purchase #2	$36.64	13.267%	$41.501	$41.50	$41.50	$41.50
Purchase #3	$84.78	11.357%	$94.4085	$94.41	$94.40	$94.40
Purchase #4	$232.74	13.782%	$264.8162	$264.82	$264.80	$264.80
Purchase #5	$58.87	11.662%	$65.7354	$65.74	$65.75	$65.70
Purchase #6	$217.41	3.193%	$224.3519	$224.35	$224.35	$224.40
Purchase #7	$104.72	4.523%	$109.4565	$109.46	$109.45	$109.50
7 purchase totals =	$912.88		$984.5829	$984.59	$984.55	$984.60