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	$52.76	12.330%	$59.2653	$59.27	$59.25	$59.30
Purchase #2	$20.60	5.489%	$21.7307	$21.73	$21.75	$21.70
Purchase #3	$125.93	12.278%	$141.3917	$141.39	$141.40	$141.40
Purchase #4	$77.98	5.848%	$82.5403	$82.54	$82.55	$82.50
Purchase #5	$200.84	10.712%	$222.354	$222.35	$222.35	$222.40
Purchase #6	$167.85	11.284%	$186.7902	$186.79	$186.80	$186.80
Purchase #7	$42.40	7.871%	$45.7373	$45.74	$45.75	$45.70
7 purchase totals =	$688.36		$759.8095	$759.81	$759.85	$759.80