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	$102.57	8.841%	$111.6382	$111.64	$111.65	$111.60
Purchase #2	$222.68	12.676%	$250.9069	$250.91	$250.90	$250.90
Purchase #3	$62.98	3.172%	$64.9777	$64.98	$65.00	$65.00
Purchase #4	$222.45	8.288%	$240.8867	$240.89	$240.90	$240.90
Purchase #5	$27.74	6.213%	$29.4635	$29.46	$29.45	$29.50
Purchase #6	$149.81	4.623%	$156.7357	$156.74	$156.75	$156.70
Purchase #7	$92.65	13.814%	$105.4487	$105.45	$105.45	$105.40
7 purchase totals =	$880.88		$960.0574	$960.07	$960.10	$960.00