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	$103.62	13.577%	$117.6885	$117.69	$117.70	$117.70
Purchase #2	$103.32	6.363%	$109.8943	$109.89	$109.90	$109.90
Purchase #3	$31.94	8.122%	$34.5342	$34.53	$34.55	$34.50
Purchase #4	$88.77	4.243%	$92.5365	$92.54	$92.55	$92.50
Purchase #5	$64.65	10.255%	$71.2799	$71.28	$71.30	$71.30
Purchase #6	$187.48	3.600%	$194.2293	$194.23	$194.25	$194.20
Purchase #7	$196.46	4.152%	$204.617	$204.62	$204.60	$204.60
7 purchase totals =	$776.24		$824.7797	$824.78	$824.85	$824.70