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	$149.56	4.711%	$156.6058	$156.61	$156.60	$156.60
Purchase #2	$157.80	8.545%	$171.284	$171.28	$171.30	$171.30
Purchase #3	$176.63	13.677%	$200.7877	$200.79	$200.80	$200.80
Purchase #4	$62.90	12.123%	$70.5254	$70.53	$70.55	$70.50
Purchase #5	$70.91	3.601%	$73.4635	$73.46	$73.45	$73.50
Purchase #6	$11.90	5.824%	$12.5931	$12.59	$12.60	$12.60
Purchase #7	$52.74	5.721%	$55.7573	$55.76	$55.75	$55.80
7 purchase totals =	$682.44		$741.0168	$741.02	$741.05	$741.10