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	$113.61	8.466%	$123.2282	$123.23	$123.25	$123.20
Purchase #2	$9.92	12.807%	$11.1905	$11.19	$11.20	$11.20
Purchase #3	$49.78	11.547%	$55.5281	$55.53	$55.55	$55.50
Purchase #4	$73.49	7.214%	$78.7916	$78.79	$78.80	$78.80
Purchase #5	$87.84	3.506%	$90.9197	$90.92	$90.90	$90.90
Purchase #6	$34.44	12.251%	$38.6592	$38.66	$38.65	$38.70
Purchase #7	$92.49	7.851%	$99.7514	$99.75	$99.75	$99.80
7 purchase totals =	$461.57		$498.0687	$498.07	$498.10	$498.10