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	$92.69	3.583%	$96.0111	$96.01	$96.00	$96.00
Purchase #2	$39.34	8.156%	$42.5486	$42.55	$42.55	$42.50
Purchase #3	$37.72	13.594%	$42.8477	$42.85	$42.85	$42.80
Purchase #4	$96.35	13.271%	$109.1366	$109.14	$109.15	$109.10
Purchase #5	$237.34	10.147%	$261.4229	$261.42	$261.40	$261.40
Purchase #6	$54.46	5.180%	$57.281	$57.28	$57.30	$57.30
Purchase #7	$194.94	8.793%	$212.0811	$212.08	$212.10	$212.10
7 purchase totals =	$752.84		$821.3290	$821.33	$821.35	$821.20