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	$224.41	10.424%	$247.8025	$247.80	$247.80	$247.80
Purchase #2	$187.25	6.870%	$200.1141	$200.11	$200.10	$200.10
Purchase #3	$196.53	6.763%	$209.8213	$209.82	$209.80	$209.80
Purchase #4	$7.25	5.374%	$7.6396	$7.64	$7.65	$7.60
Purchase #5	$38.62	5.855%	$40.8812	$40.88	$40.90	$40.90
Purchase #6	$77.40	4.304%	$80.7313	$80.73	$80.75	$80.70
Purchase #7	$73.91	11.730%	$82.5796	$82.58	$82.60	$82.60
7 purchase totals =	$805.37		$869.5696	$869.56	$869.60	$869.50