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	$240.54	5.455%	$253.6615	$253.66	$253.65	$253.70
Purchase #2	$67.78	6.487%	$72.1769	$72.18	$72.20	$72.20
Purchase #3	$154.92	7.859%	$167.0952	$167.10	$167.10	$167.10
Purchase #4	$84.34	5.385%	$88.8817	$88.88	$88.90	$88.90
Purchase #5	$65.89	10.330%	$72.6964	$72.70	$72.70	$72.70
Purchase #6	$60.94	3.217%	$62.9004	$62.90	$62.90	$62.90
Purchase #7	$56.98	12.221%	$63.9435	$63.94	$63.95	$63.90
7 purchase totals =	$731.39		$781.3556	$781.36	$781.40	$781.40