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	$89.35	5.696%	$94.4394	$94.44	$94.45	$94.40
Purchase #2	$102.26	3.201%	$105.5333	$105.53	$105.55	$105.50
Purchase #3	$103.69	5.220%	$109.1026	$109.10	$109.10	$109.10
Purchase #4	$34.40	13.443%	$39.0244	$39.02	$39.00	$39.00
Purchase #5	$190.29	10.526%	$210.3199	$210.32	$210.30	$210.30
Purchase #6	$102.27	10.224%	$112.7261	$112.73	$112.75	$112.70
Purchase #7	$107.77	5.224%	$113.3999	$113.40	$113.40	$113.40
7 purchase totals =	$730.03		$784.5456	$784.54	$784.55	$784.40