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	$174.85	6.581%	$186.3569	$186.36	$186.35	$186.40
Purchase #2	$220.41	4.600%	$230.5489	$230.55	$230.55	$230.50
Purchase #3	$32.95	4.787%	$34.5273	$34.53	$34.55	$34.50
Purchase #4	$19.87	6.830%	$21.2271	$21.23	$21.25	$21.20
Purchase #5	$94.91	9.417%	$103.8477	$103.85	$103.85	$103.80
Purchase #6	$59.62	3.728%	$61.8426	$61.84	$61.85	$61.80
Purchase #7	$93.28	11.308%	$103.8281	$103.83	$103.85	$103.80
7 purchase totals =	$695.89		$742.1786	$742.19	$742.25	$742.00