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	$159.89	4.522%	$167.1202	$167.12	$167.10	$167.10
Purchase #2	$97.78	8.418%	$106.0111	$106.01	$106.00	$106.00
Purchase #3	$78.44	5.174%	$82.4985	$82.50	$82.50	$82.50
Purchase #4	$93.30	13.552%	$105.944	$105.94	$105.95	$105.90
Purchase #5	$59.50	9.417%	$65.1031	$65.10	$65.10	$65.10
Purchase #6	$31.59	3.173%	$32.5924	$32.59	$32.60	$32.60
Purchase #7	$12.78	3.755%	$13.2599	$13.26	$13.25	$13.30
7 purchase totals =	$533.28		$572.5292	$572.52	$572.50	$572.50