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	$211.96	8.433%	$229.8346	$229.83	$229.85	$229.80
Purchase #2	$9.49	3.869%	$9.8572	$9.86	$9.85	$9.90
Purchase #3	$41.55	10.111%	$45.7511	$45.75	$45.75	$45.80
Purchase #4	$70.62	13.711%	$80.3027	$80.30	$80.30	$80.30
Purchase #5	$83.28	8.543%	$90.3946	$90.39	$90.40	$90.40
Purchase #6	$144.45	13.552%	$164.0259	$164.03	$164.05	$164.00
Purchase #7	$25.25	13.370%	$28.6259	$28.63	$28.65	$28.60
7 purchase totals =	$586.60		$648.7920	$648.79	$648.85	$648.80