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	$221.30	5.564%	$233.6131	$233.61	$233.60	$233.60
Purchase #2	$77.26	3.482%	$79.9502	$79.95	$79.95	$80.00
Purchase #3	$32.86	7.518%	$35.3304	$35.33	$35.35	$35.30
Purchase #4	$169.51	12.575%	$190.8259	$190.83	$190.85	$190.80
Purchase #5	$99.57	7.323%	$106.8615	$106.86	$106.85	$106.90
Purchase #6	$193.40	12.628%	$217.8226	$217.82	$217.80	$217.80
Purchase #7	$124.88	13.319%	$141.5128	$141.51	$141.50	$141.50
7 purchase totals =	$918.78		$1,005.9165	$1,005.91	$1,005.90	$1,005.90