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	$221.56	12.279%	$248.7654	$248.77	$248.75	$248.80
Purchase #2	$127.98	11.356%	$142.5134	$142.51	$142.50	$142.50
Purchase #3	$217.35	5.212%	$228.6783	$228.68	$228.70	$228.70
Purchase #4	$98.93	13.781%	$112.5635	$112.56	$112.55	$112.60
Purchase #5	$62.32	12.103%	$69.8626	$69.86	$69.85	$69.90
Purchase #6	$104.63	13.328%	$118.5751	$118.58	$118.60	$118.60
Purchase #7	$155.44	3.208%	$160.4265	$160.43	$160.45	$160.40
7 purchase totals =	$988.21		$1,081.3848	$1,081.39	$1,081.40	$1,081.50