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	$42.97	3.398%	$44.4301	$44.43	$44.45	$44.40
Purchase #2	$103.25	9.739%	$113.3055	$113.31	$113.30	$113.30
Purchase #3	$72.64	8.447%	$78.7759	$78.78	$78.80	$78.80
Purchase #4	$153.76	9.113%	$167.7721	$167.77	$167.75	$167.80
Purchase #5	$192.93	4.351%	$201.3244	$201.32	$201.30	$201.30
Purchase #6	$51.27	4.802%	$53.732	$53.73	$53.75	$53.70
Purchase #7	$59.56	4.280%	$62.1092	$62.11	$62.10	$62.10
7 purchase totals =	$676.38		$721.4492	$721.45	$721.45	$721.40