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	$50.43	6.512%	$53.714	$53.71	$53.70	$53.70
Purchase #2	$57.72	6.710%	$61.593	$61.59	$61.60	$61.60
Purchase #3	$39.79	12.811%	$44.8875	$44.89	$44.90	$44.90
Purchase #4	$27.54	9.308%	$30.1034	$30.10	$30.10	$30.10
Purchase #5	$52.42	6.563%	$55.8603	$55.86	$55.85	$55.90
Purchase #6	$249.34	6.170%	$264.7243	$264.72	$264.70	$264.70
Purchase #7	$75.98	9.154%	$82.9352	$82.94	$82.95	$82.90
7 purchase totals =	$553.22		$593.8177	$593.81	$593.80	$593.80