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	$144.38	13.655%	$164.0951	$164.10	$164.10	$164.10
Purchase #2	$125.63	11.219%	$139.7244	$139.72	$139.70	$139.70
Purchase #3	$103.54	3.119%	$106.7694	$106.77	$106.75	$106.80
Purchase #4	$210.57	13.427%	$238.8432	$238.84	$238.85	$238.80
Purchase #5	$108.30	11.382%	$120.6267	$120.63	$120.65	$120.60
Purchase #6	$183.27	7.121%	$196.3207	$196.32	$196.30	$196.30
Purchase #7	$144.30	5.348%	$152.0172	$152.02	$152.00	$152.00
7 purchase totals =	$1,019.99		$1,118.3967	$1,118.40	$1,118.35	$1,118.30