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	$178.73	9.706%	$196.0775	$196.08	$196.10	$196.10
Purchase #2	$128.40	13.412%	$145.621	$145.62	$145.60	$145.60
Purchase #3	$210.48	5.657%	$222.3869	$222.39	$222.40	$222.40
Purchase #4	$70.70	10.283%	$77.9701	$77.97	$77.95	$78.00
Purchase #5	$225.99	8.821%	$245.9246	$245.92	$245.90	$245.90
Purchase #6	$92.96	5.714%	$98.2717	$98.27	$98.25	$98.30
Purchase #7	$71.64	4.177%	$74.6324	$74.63	$74.65	$74.60
7 purchase totals =	$978.90		$1,060.8842	$1,060.88	$1,060.85	$1,060.90