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	$54.91	13.817%	$62.4969	$62.50	$62.50	$62.50
Purchase #2	$73.55	13.734%	$83.6514	$83.65	$83.65	$83.70
Purchase #3	$78.81	11.545%	$87.9086	$87.91	$87.90	$87.90
Purchase #4	$190.45	3.270%	$196.6777	$196.68	$196.70	$196.70
Purchase #5	$153.34	5.751%	$162.1586	$162.16	$162.15	$162.20
Purchase #6	$150.97	11.589%	$168.4659	$168.47	$168.45	$168.50
Purchase #7	$150.73	13.267%	$170.7273	$170.73	$170.75	$170.70
7 purchase totals =	$852.76		$932.0864	$932.10	$932.10	$932.20