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	$59.39	13.276%	$67.2746	$67.27	$67.25	$67.30
Purchase #2	$236.97	3.446%	$245.136	$245.14	$245.15	$245.10
Purchase #3	$44.60	10.170%	$49.1358	$49.14	$49.15	$49.10
Purchase #4	$146.82	11.677%	$163.9642	$163.96	$163.95	$164.00
Purchase #5	$184.72	3.755%	$191.6562	$191.66	$191.65	$191.70
Purchase #6	$195.86	13.577%	$222.4519	$222.45	$222.45	$222.50
Purchase #7	$160.65	5.501%	$169.4874	$169.49	$169.50	$169.50
7 purchase totals =	$1,029.01		$1,109.1061	$1,109.11	$1,109.10	$1,109.20