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	$221.26	6.270%	$235.133	$235.13	$235.15	$235.10
Purchase #2	$69.31	12.295%	$77.8317	$77.83	$77.85	$77.80
Purchase #3	$182.66	7.353%	$196.091	$196.09	$196.10	$196.10
Purchase #4	$147.46	10.351%	$162.7236	$162.72	$162.70	$162.70
Purchase #5	$202.42	5.426%	$213.4033	$213.40	$213.40	$213.40
Purchase #6	$118.88	12.419%	$133.6437	$133.64	$133.65	$133.60
Purchase #7	$79.96	13.682%	$90.9001	$90.90	$90.90	$90.90
7 purchase totals =	$1,021.95		$1,109.7264	$1,109.71	$1,109.75	$1,109.60