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	$215.66	10.674%	$238.6795	$238.68	$238.70	$238.70
Purchase #2	$64.77	4.794%	$67.8751	$67.88	$67.90	$67.90
Purchase #3	$94.43	11.324%	$105.1233	$105.12	$105.10	$105.10
Purchase #4	$41.69	11.539%	$46.5006	$46.50	$46.50	$46.50
Purchase #5	$160.82	8.154%	$173.9333	$173.93	$173.95	$173.90
Purchase #6	$42.92	9.248%	$46.8892	$46.89	$46.90	$46.90
Purchase #7	$213.63	4.721%	$223.7155	$223.72	$223.70	$223.70
7 purchase totals =	$833.92		$902.7165	$902.72	$902.75	$902.70