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	$108.78	13.149%	$123.0835	$123.08	$123.10	$123.10
Purchase #2	$150.91	11.346%	$168.0322	$168.03	$168.05	$168.00
Purchase #3	$52.43	4.837%	$54.966	$54.97	$54.95	$55.00
Purchase #4	$103.31	7.337%	$110.8899	$110.89	$110.90	$110.90
Purchase #5	$67.66	5.310%	$71.2527	$71.25	$71.25	$71.30
Purchase #6	$79.43	7.613%	$85.477	$85.48	$85.50	$85.50
Purchase #7	$79.61	3.129%	$82.101	$82.10	$82.10	$82.10
7 purchase totals =	$642.13		$695.8023	$695.80	$695.85	$695.90