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	$150.61	11.874%	$168.4934	$168.49	$168.50	$168.50
Purchase #2	$31.65	5.500%	$33.3908	$33.39	$33.40	$33.40
Purchase #3	$96.59	5.630%	$102.028	$102.03	$102.05	$102.00
Purchase #4	$51.25	9.259%	$55.9952	$56.00	$56.00	$56.00
Purchase #5	$59.37	10.130%	$65.3842	$65.38	$65.40	$65.40
Purchase #6	$43.58	4.267%	$45.4396	$45.44	$45.45	$45.40
Purchase #7	$243.73	8.577%	$264.6347	$264.63	$264.65	$264.60
7 purchase totals =	$676.78		$735.3659	$735.36	$735.45	$735.30