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	$149.28	3.372%	$154.3137	$154.31	$154.30	$154.30
Purchase #2	$215.48	3.351%	$222.7007	$222.70	$222.70	$222.70
Purchase #3	$34.65	13.670%	$39.3867	$39.39	$39.40	$39.40
Purchase #4	$200.42	11.581%	$223.6306	$223.63	$223.65	$223.60
Purchase #5	$6.73	13.516%	$7.6396	$7.64	$7.65	$7.60
Purchase #6	$132.69	7.116%	$142.1322	$142.13	$142.15	$142.10
Purchase #7	$83.36	8.336%	$90.3089	$90.31	$90.30	$90.30
7 purchase totals =	$822.61		$880.1124	$880.11	$880.15	$880.00