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	$49.50	9.148%	$54.0283	$54.03	$54.05	$54.00
Purchase #2	$33.46	12.838%	$37.7556	$37.76	$37.75	$37.80
Purchase #3	$88.60	12.698%	$99.8504	$99.85	$99.85	$99.90
Purchase #4	$221.47	7.675%	$238.4678	$238.47	$238.45	$238.50
Purchase #5	$229.37	3.497%	$237.3911	$237.39	$237.40	$237.40
Purchase #6	$193.62	5.307%	$203.8954	$203.90	$203.90	$203.90
Purchase #7	$176.31	12.574%	$198.4792	$198.48	$198.50	$198.50
7 purchase totals =	$992.33		$1,069.8678	$1,069.88	$1,069.90	$1,070.00